├── LICENSE ├── README.md ├── database └── README.md ├── distributed system └── README.md ├── framework └── README.md └── img ├── MySQL命令行查看版本号.jpg ├── README.md ├── Solr.png ├── Spring Framework.jpg ├── Spring组件.png ├── status查看版本号.jpg └── 系统函数查看版本号.jpg /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. 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Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # 关于 2 | 3 | - 本仓库将以面试题为导向，将 Java 后台开发面试中遇到的问题和解题思路或答案整理输出，一方面是为了方便自己复盘，另一方面也是希望对其他胖友能有所帮助； 4 | - 由于水平有限，本仓库中部分题目来源于面试所遇，一部分源于网上； 5 | - 面试题只是为了让我们在学习这些技术的时候知道如何抓住重点，但不能只浮于表面，而是要稳扎稳打，把基础打牢，勿在浮沙筑高台； 6 | - 源码之中，了无秘密，即使现在没有太多源码阅读的经验，后续也一定要多多阅读源码。 7 | - TODO：后续会依次整理部分题目的参考解答思路，整理的目的是为了后续更深入地学习一个技术，而不是让大家背答案！ 8 | 9 | # 前言 10 | 11 | - 整理不易，如果觉得有帮助请点个 `star` 12 | 13 | # 目录 14 | 15 | ## Java基础 16 | ## Java并发 17 | ## JVM 18 | ## 框架 19 | - [Spring](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring) 20 | - [Spring Framework](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-framework) 21 | - [Spring Bean](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-bean) 22 | - [Spring IoC](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-ioc) 23 | - [Spring 注解](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-%E6%B3%A8%E8%A7%A3) 24 | - [Spring AOP](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-aop) 25 | - [Spring 事务](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring-%E4%BA%8B%E5%8A%A1) 26 | - [SpringMVC](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#springmvc) 27 | - [Mybatis](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#mybatis) 28 | - [SpringBoot](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#springboot) 29 | - [Hibernate](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#hibernate) 30 | ## 分布式系统 31 | ### 分布式缓存 32 | - Memcached 33 | - [Redis](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#redis) 34 | 35 | ### 分布式服务框架 36 | - Dubbo 37 | 38 | ### 分布式协调服务 39 | - Zookeeper 40 | 41 | ### 分布式消息队列 42 | - RabbitMQ 43 | - Kafka 44 | 45 | ### 分布式搜索引擎 46 | 47 | - [Elasticsearch](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#elasticsearch) 48 | - [Solr](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#solr) 49 | 50 | ### 分布式事务 51 | 52 | ## 数据库 53 | - [MySQL](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#mysql) 54 | 55 | ## 设计模式 56 | ## 数据结构和算法 57 | - 详见[链接](https://github.com/bigrotor187/awesome-java-notes#%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95) 58 | -------------------------------------------------------------------------------- /database/README.md: -------------------------------------------------------------------------------- 1 | # MySQL 学习笔记 2 | 3 | ## 《MySQL是怎样运行的——从根儿上理解MySQL》 4 | 5 | - [1、MySQL 概述]() 6 | - [2、MySQL 查询请求执行过程]() 7 | - [3、常用存储引擎]() 8 | - [4、字符集和比较规则]() 9 | - [5、InnoDB 是如何存储一条数据记录的？]() 10 | - [6、InnoDB 数据页结构]() 11 | - [7、快速查询的秘籍——B+ 树索引简介]() 12 | - [8、B+ 树索引是如何使用的？]() 13 | - [9、MySQL 的数据目录]() 14 | - [10、存放页面的大池子——InnoDB 的表空间]() 15 | - [11、MySQL 单表是如何访问的？]() 16 | - [12、连接的原理及查询成本的优化]() 17 | - [13、MySQL 基于规则的优化与子查询优化]() 18 | - [14、EXPLAIN 详解]() 19 | - [15、InnoDB 的 Buffer Pool——条件磁盘和 CPU 的矛盾]() 20 | - [16、MySQL 事务简介]() 21 | - [17、redo 日志]() 22 | - [18、undo 日志]() 23 | - [19、事务隔离级别和 MVCC]() 24 | - [20、面试老大难——锁]() 25 | 26 | 27 | # MySQL 实战案例 28 | - [1、MySQL 加锁分析](http://www.fanyilun.me/2017/04/20/MySQL%E5%8A%A0%E9%94%81%E5%88%86%E6%9E%90/) 29 | - [2、常见 MySQL 死锁案例](https://github.com/aneasystone/mysql-deadlocks) 30 | 31 | 32 | # MySQL 面试问题 33 | 34 | - [1、数据库的三范式是什么？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#1%E6%95%B0%E6%8D%AE%E5%BA%93%E7%9A%84%E4%B8%89%E8%8C%83%E5%BC%8F%E6%98%AF%E4%BB%80%E4%B9%88) 35 | - [2、一张自增表里面总共有 7 条数据，删除了最后 2 条数据，重启 mysql 数据库，又插入了一条数据，此时 id 是几？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#2%E4%B8%80%E5%BC%A0%E8%87%AA%E5%A2%9E%E8%A1%A8%E9%87%8C%E9%9D%A2%E6%80%BB%E5%85%B1%E6%9C%89-7-%E6%9D%A1%E6%95%B0%E6%8D%AE%E5%88%A0%E9%99%A4%E4%BA%86%E6%9C%80%E5%90%8E-2-%E6%9D%A1%E6%95%B0%E6%8D%AE%E9%87%8D%E5%90%AF-mysql-%E6%95%B0%E6%8D%AE%E5%BA%93%E5%8F%88%E6%8F%92%E5%85%A5%E4%BA%86%E4%B8%80%E6%9D%A1%E6%95%B0%E6%8D%AE%E6%AD%A4%E6%97%B6-id-%E6%98%AF%E5%87%A0) 36 | - [3、如何获取当前数据库版本？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#3%E5%A6%82%E4%BD%95%E8%8E%B7%E5%8F%96%E5%BD%93%E5%89%8D%E6%95%B0%E6%8D%AE%E5%BA%93%E7%89%88%E6%9C%AC) 37 | - [4、说一下 ACID 是什么？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#4%E8%AF%B4%E4%B8%80%E4%B8%8B-acid-%E6%98%AF%E4%BB%80%E4%B9%88) 38 | - [5、char 和 varchar 的区别是什么？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#5char-%E5%92%8C-varchar-%E7%9A%84%E5%8C%BA%E5%88%AB%E6%98%AF%E4%BB%80%E4%B9%88) 39 | - [6、float 和 double 的区别是什么？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#6float-%E5%92%8C-double-%E7%9A%84%E5%8C%BA%E5%88%AB%E6%98%AF%E4%BB%80%E4%B9%88) 40 | - [7、mysql 的内连接、左连接、右连接有什么区别？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#7mysql-%E7%9A%84%E5%86%85%E8%BF%9E%E6%8E%A5%E5%B7%A6%E8%BF%9E%E6%8E%A5%E5%8F%B3%E8%BF%9E%E6%8E%A5%E6%9C%89%E4%BB%80%E4%B9%88%E5%8C%BA%E5%88%AB) 41 | - [8、mysql 索引是怎么实现的？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#8mysql-%E7%B4%A2%E5%BC%95%E6%98%AF%E6%80%8E%E4%B9%88%E5%AE%9E%E7%8E%B0%E7%9A%84) 42 | - [9、怎么验证 mysql 的索引是否满足需求？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#9%E6%80%8E%E4%B9%88%E9%AA%8C%E8%AF%81-mysql-%E7%9A%84%E7%B4%A2%E5%BC%95%E6%98%AF%E5%90%A6%E6%BB%A1%E8%B6%B3%E9%9C%80%E6%B1%82) 43 | - [10、说一下数据库的事务隔离？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#10%E8%AF%B4%E4%B8%80%E4%B8%8B%E6%95%B0%E6%8D%AE%E5%BA%93%E7%9A%84%E4%BA%8B%E5%8A%A1%E9%9A%94%E7%A6%BB) 44 | - [11、说一下 mysql 常用的引擎？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#11%E8%AF%B4%E4%B8%80%E4%B8%8B-mysql-%E5%B8%B8%E7%94%A8%E7%9A%84%E5%BC%95%E6%93%8E) 45 | - [12、说一下 mysql 的行锁和表锁？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#12%E8%AF%B4%E4%B8%80%E4%B8%8B-mysql-%E7%9A%84%E8%A1%8C%E9%94%81%E5%92%8C%E8%A1%A8%E9%94%81) 46 | - [13、说一下乐观锁和悲观锁？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#13%E8%AF%B4%E4%B8%80%E4%B8%8B%E4%B9%90%E8%A7%82%E9%94%81%E5%92%8C%E6%82%B2%E8%A7%82%E9%94%81) 47 | - [14、mysql 问题排查都有哪些手段？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#14mysql-%E9%97%AE%E9%A2%98%E6%8E%92%E6%9F%A5%E9%83%BD%E6%9C%89%E5%93%AA%E4%BA%9B%E6%89%8B%E6%AE%B5) 48 | - [15、如何做 mysql 的性能优化？](https://github.com/bigrotor187/awesome-java-interview/tree/master/database#15%E5%A6%82%E4%BD%95%E5%81%9A-mysql-%E7%9A%84%E6%80%A7%E8%83%BD%E4%BC%98%E5%8C%96) 49 | 50 | ## 1、数据库的三范式是什么？ 51 | - **第一范式:** 每个列都不可以再拆分。 52 | 53 | - **第二范式:** 非主键列完全依赖于主键,而不能是依赖于主键的一部分.。 54 | 55 | - **第三范式:** 非主键列只依赖于主键,不依赖于其他非主键。 56 | 57 | 在设计数据库结构的时候，要尽量遵守三范式，如果不遵守，必须有足够的理由，比如性能。事实上我们经常会为了性能而妥协数据库的设计。 58 | 59 | ## 2、一张自增表里面总共有 7 条数据，删除了最后 2 条数据，重启 mysql 数据库，又插入了一条数据，此时 id 是几？ 60 | - 一般情况下，MySQL 中创建表的类型为 InnoDB，如果新增一条记录（在 MySQL 不重启的情况下），这条记录的 ID 为 8；但是，如果**重启 MySQL 的情况下**，那么这条记录的 ID 为 61 | 6，因为 InnoDB 表只把自增主键的最大 ID 记录到内存中，所以重启数据库或者对表执行 OPTIMIZE 操作，都会使最大 ID 丢失。 62 | - 如果我们设置表的类型是 MyISAM，那么这条记录的 ID 就是 8。因为MylSAM表会把自增主键的最大ID记录到数据文件里面，重启MYSQL后，自增主键的最大ID也不会丢失。 63 | - 如果在这 7 条记录里面删除的是中间的几个记录（比如删除的是 3,4,5 三条记录），重启 MySQL 数据库后，insert 一条记录后，ID 都是 8。因为内存或者数据库文件存储的都是自增主键的最大 ID。 64 | 65 | ## 3、如何获取当前数据库版本？ 66 | - 一、使用命令行模式进入mysql会看到最开始的提示符： 67 | 68 | ![](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/MySQL%E5%91%BD%E4%BB%A4%E8%A1%8C%E6%9F%A5%E7%9C%8B%E7%89%88%E6%9C%AC%E5%8F%B7.jpg) 69 | 70 | - 二、命令行中使用 status 可以查看： 71 | 72 | ![](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/status%E6%9F%A5%E7%9C%8B%E7%89%88%E6%9C%AC%E5%8F%B7.jpg) 73 | 74 | - 三、使用系统函数 version()： 75 | 76 | ![](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/%E7%B3%BB%E7%BB%9F%E5%87%BD%E6%95%B0%E6%9F%A5%E7%9C%8B%E7%89%88%E6%9C%AC%E5%8F%B7.jpg) 77 | 78 | ## 4、说一下 ACID 是什么？ 79 | 80 | - ACID 指的是事务 的四大特性，分别是`原子性（Atomicity）`、`一致性（Consistency）`、`隔离性（Isolation）`、`永久性（Durability）`。 81 | - **原子性：** 原子性是指事务是一个不可分割的工作单位，事务中的操作要么全部成功，要么全部失败。比如在同一个事务中的SQL语句，要么全部执行成功，要么全部执行失败。 82 | - **一致性：** 官网上事务一致性的概念是：事务必须使数据库从一个一致性状态变换到另外一个一致性状态。以转账为例子，A向B转账，假设转账之前这两个用户的钱加起来总共是2000，那么A向B转账之后，不管这两个账户怎么转，A用户的钱和B用户的钱加起来的总额还是2000，这个就是事务的一致性。 83 | - **隔离性：** 事务的隔离性是多个用户并发访问数据库时，数据库为每一个用户开启的事务，不能被其他事务的操作数据所干扰，多个并发事务之间要相互隔离。 84 | - **永久性：** 持久性是指一个事务一旦被提交，它对数据库中数据的改变就是永久性的，接下来即使数据库发生故障也不应该对其有任何影响。 85 | 86 | ## 5、char 和 varchar 的区别是什么？ 87 | 88 | - **是否是定长的：** char 是一个定长字段，假如申请了char(10) 的空间，那么无论实际存储多少内容，该字段都占用 10 个字符。而 varchar 是变长的，也就是说申请的只是最大长度，占用的空间为实际字符长度 +1，最后一个字符存储使用了多长的空间。 89 | 90 | - **从检索效率上来讲**，char > varchar，因此在使用中如果确定某个字段的值的长度，可以使用 char，否则应该尽量使用 varchar。例如存储用户MD5加密后的密码，则应该使用 char。 91 | 92 | ## 6、float 和 double 的区别是什么？ 93 | 94 | - float类型表示单精度浮点数值，double类型表示双精度浮点数值，float和double都是浮点型，而decimal是定点型； 95 | - MySQL 浮点型和定点型可以用类型名称后加（M，D）来表示，M表示该值的总共长度，D表示小数点后面的长度，M和D又称为精度和标度，如float(5,2)的 可显示为999.99，MySQL保存值时会进行四舍五入，如果插入999.009，则结果为999.01。 96 | - float和double在不指定精度时，默认会按照实际的精度来显示，而DECIMAL在不指定精度时，默认整数为10，小数为0。 97 | 98 | > 具体可参考：https://blog.csdn.net/lihua5419/article/details/81316914 99 | 100 | ## 7、MySQL 的内连接、左连接、右连接有什么区别？ 101 | 102 | - 左连接：左边有的，右边没有的为 null 103 | 104 | - 右连接：左边没有的，右边有的为 null 105 | 106 | - 内连接：显示左边右边共有的 107 | 108 | > 具体请移步: https://blog.csdn.net/wang0112233/article/details/78418698 109 | 110 | ## 8、MySQL 索引是如何实现的？ 111 | 112 | - 索引的数据结构和具体的数据库存储引擎的实现有关，在 MySQL 中使用较多的索引有哈希索引、BTree索引等。其中，哈希索引底层数据结构使用的是哈希表，而BTree索引使用的是B树中的B+Tree。在 MySQL 中，经常使用的 InnoDB 存储引擎的默认索引实现为：BTree索引。 113 | - 创建索引时，建议对如下情况创建： 114 | - 出现在 SELECT、UPDATE、DELETE 语句的 WHERE 从句中的列 115 | - 包含在 ORDER BY、GROUP BY、DISTINCT 中的字段 116 | - 并不要将符合 1 和 2 中的字段的列都建立一个索引， 通常将 1、2 中的字段建立联合索引效果更好 117 | - 多表 join 的关联列 118 | 119 | 常见的索引类型有：主键索引、唯一索引、普通索引、全文索引、组合索引 120 | 121 | 1、主键索引：即主索引，根据主键pk_clolum（length）建立索引，不允许重复，不允许空值； 122 | `ALTER TABLE `table_name` ADD PRIMARY KEY (`column`);` 123 | 124 | 2、唯一索引：用来建立索引的列的值必须是唯一的，允许空值 125 | `ALTER TABLE `table_name` ADD UNIQUE (`column`) ;` 126 | 127 | 3、普通索引：用表中的普通列构建的索引，没有任何限制 128 | `ALTER TABLE `table_name` ADD INDEX index_name (`column`);` 129 | 130 | 4、全文索引：用大文本对象的列构建的索引 131 | `ALTER TABLE `table_name` ADD FULLTEXT (`column`);` 132 | 133 | 5、组合索引：用多个列组合构建的索引，这多个列中的值不允许有空值 134 | `ALTER TABLE `table_name` ADD INDEX index_name (`column1`, `column2`, `column3`);` 135 | 136 | ## 9、怎么验证 MySQL 的索引是否满足需求？或者换个说法，如何判断创建的索引有没有被使用到?或者说怎么才可以知道这条语句运行很慢的原因? 137 | 138 | 需要根据查询需求来决定配置索引的类型，一旦确定索引类型之后，可以使用 EXPLAIN 查看 SQL 执行计划，确认索引是否满足需求。 139 | 140 | - MySQL提供了 EXPLAIN 命令来查看语句的执行计划，MySQL在执行某个语句之前，会将该语句过一遍查询优化器，之后会拿到对语句的分析,也就是执行计划，其中包含了许多信息。可以通过其中和索引有关的信息来分析是否命中了索引，例如 possilbe_key，key，key_len 等字段,分别说明了此语句可能会使用的索引，实际使用的索引以及使用的索引长度。具体过程如下: 141 | 142 | - 在 select 语句前加上 explain 就可以用来查看 sql 的执行计划，EXPLAIN 显示了 MySQL 如何使用索引来处理 select 语句以及连接表; 143 | 144 | - possible_keys：显示可能应用在这张表中的索引。如果为空，没有可能的索引。可以为相关的域从WHERE语句中选择一个合适的语句 145 | 146 | - key： 实际使用的索引。如果为 NULL，则没有使用索引。很少的情况下，MySQL 会选择优化不足的索引。这种情况下，可以在 SELECT 语句中使用 USE INDEX(indexname) 来强制使用一个索引或者用IGNORE INDEX(indexname)来强制MYSQL忽略索引 147 | 148 | 最后,虽然 EXPLAIN 可以检查我们的 SQL 索引命中情况，但实际上线后，最好配合监控来看下接口的 RT。 149 | 150 | ## 10、说一下数据库的事务隔离？ 151 | 152 | 多个线程开启各自事务操作数据库中数据时，数据库系统要负责隔离操作，以保证各个线程在获取数据时的准确性。 153 | 154 | **1、事务不考虑隔离性可能会引发的问题** 155 | 156 | 如果事务不考虑隔离性，可能会引发如下问题： 157 | 158 | - （1）脏读 159 | 脏读指一个事务读取了另外一个事务未提交的数据。 160 | 161 | 这是非常危险的，假设Ａ向Ｂ转帐100元，对应sql语句如下所示 162 | 163 | ```java 164 | 1.update account set money=money+100 where name='B'; 165 | 2.update account set money=money-100 where name='A'; 166 | ``` 167 | 当第1条 SQL 执行完，第2条还没执行(A 未提交时)，如果此时 Ｂ 查询自己的帐户，就会发现自己多了 100 元钱。如果 A 等 B 走后再回滚，B 就会损失 100 元。 168 | 169 | - （2）不可重复读 170 | 不可重复读指在一个事务内读取表中的某一行数据，多次读取结果不同。 171 | 172 | 例如银行想查询 A 帐户余额，第一次查询A帐户为 200 元，此时A向帐户内存了 100 元并提交了，银行接着又进行了一次查询，此时 A 帐户为 300 元了。银行两次查询不一致，可能就会很困惑，不知道哪次查询是准的。 173 | 174 | 不可重复读和脏读的区别是，脏读是读取前一事务未提交的脏数据，不可重复读是重新读取了前一事务已提交的数据。 175 | 176 | 很多人认为这种情况就对了，无须困惑，当然是后面的为准。我们可以考虑这样一种情况，比如银行程序需要将查询结果分别输出到电脑屏幕和写到文件中，结果在一个事务中针对输出的目的地，进行的两次查询不一致，导致文件和屏幕中的结果不一致，银行工作人员就不知道以哪个为准了。 177 | 178 | - （3）虚读(幻读) 179 | 虚读(幻读)是指在一个事务内读取到了别的事务插入的数据，导致前后读取不一致。 180 | 181 | 如丙存款 100 元未提交，这时银行做报表统计 account 表中所有用户的总额为 500 元，然后丙提交了，这时银行再统计发现帐户为 600 元了，造成虚读同样会使银行不知所措，到底以哪个为准。 182 | 183 | 注：以下为在原文的基础上补充的部分 184 | 185 | - （4）丢失修改 186 | 丢失修改（Lost to modify）是指在一个事务读取一个数据时，另外一个事务也访问了该数据，那么在第一个事务中修改了这个数据后，第二个事务也修改了这个数据。这样第一个事务内的修改结果就被丢失，因此称为丢失修改。 187 | 188 | 例如：事务 1 读取某表中的数据 A=20，事务 2 也读取 A=20，事务 1 修改 A=A-1，事务 2 也修改 A=A-1，最终结果 A=19，事务 1 的修改被丢失。 189 | 190 | *不可重复读和幻读区别：* 191 | 192 | 不可重复读的重点是修改，比如多次读取一条记录发现其中某些列的值被修改；幻读的重点在于新增或者删除，比如多次读取一条记录发现记录增多或减少了。 193 | 194 | ## 11、说一下 MySQL 常用的引擎？ 195 | 196 | MySQL 常用的引擎主要有`InnoDB`和`MyISQM`两种，其中，在 5.5 版本之前，`MyISAM`是 MySQL 默认的数据库引擎，而 5.5 版本之后默认的数据库引擎是`InnoDB`。`MyISAM`强调的是性能，性能极佳，并且提供了大量的特性，比如全文索引、压缩、空间函数等，但是`MyISAM`不支持事务和行级锁，最大的缺陷就是不支持崩溃后的安全恢复。两者的区别主要如下： 197 | - **是否支持行级锁** : MyISAM 只有表级锁(table-level locking)，而InnoDB 支持行级锁(row-level locking)和表级锁，默认为行级锁； 198 | - **是否支持外键**： MyISAM不支持，而InnoDB支持； 199 | - **是否支持事务和崩溃后的安全恢复**：MyISAM 强调的是性能，每次查询具有原子性,其执行速度比 InnoDB 类型更快，但是不提供事务支持。而 InnoDB 提供事务支持，外键等高级数据库功能。 具有事务(commit)、回滚(rollback)和崩溃修复能力(crash recovery capabilities)的事务安全(transaction-safe (ACID compliant))型表。 200 | - **是否支持MVCC**：仅 InnoDB 支持 MVCC。应对高并发事务，MVCC比单纯的加锁更高效；MVCC只在 READ COMMITTED 和 REPEATABLE READ 两个隔离级别下工作；MVCC可以使用`乐观(optimistic)锁`和`悲观(pessimistic)锁`来实现；各数据库中MVCC实现并不统一。 201 | 202 | **那么这两种数据库引擎要如何选择呢？** 203 | 204 | - 一般情况下选择 InnoDB 都是没有问题的，但是某些情况下如果并不在乎可扩展能力和并发能力，也不需要事务支持，也不在乎崩溃后的安全恢复问题的话，选择 MyISAM 也是一个不错的选择。但是一般情况下，我们都是需要考虑到这些问题的。 205 | 206 | ## 12、说一下 MySQL 的行级锁和表级锁？ 207 | 208 | - MyISAM 默认采用的是表级锁（table-level locking），而 InnoDB 支持行级锁（row-level locking）和表级锁，但默认采用的是行级锁。 209 | - **表级锁：** MySQL 中锁定`粒度最大`的一种锁，对当前操作的整张表加锁，实现简单，资源消耗也比较少，加锁快，不会出现死锁。其锁定粒度最大，触发锁冲突的概率最高，并发度最低，MyISAM和 InnoDB引擎都支持表级锁。 210 | - **行级锁：** MySQL中锁定`粒度最小`的一种锁，只针对当前操作的行进行加锁。 行级锁能大大减少数据库操作的冲突。其加锁粒度最小，并发度高，但加锁的开销也最大，加锁慢，会出现死锁。 211 | 212 | **InnoDB 引擎中锁的算法有三种：** 213 | - Record lock：单个行记录上的锁 214 | - Gap lock：间隙锁，锁定一个范围，不包括记录本身 215 | - Next-key lock：record+gap 锁定一个范围，包含记录本身 216 | 217 | ## 13、说一下乐观锁和悲观锁？ 218 | 219 | **乐观锁** 220 | 221 | - 乐观锁不是数据库自带的，需要我们自己去实现。乐观锁是指操作数据库时(更新操作)，想法很乐观，认为这次的操作不会导致冲突，在操作数据时，并不进行任何其他的特殊处理（也就是不加锁），而在进行更新后，再去判断是否有冲突了。 222 | 223 | - 通常实现是这样的：在表中的数据进行操作时(更新)，先给数据表加一个版本(version)字段，每操作一次，将那条记录的版本号加1。也就是先查询出那条记录，获取出version字段,如果要对那条记录进行操作(更新),则先判断此刻version的值是否与刚刚查询出来时的version的值相等，如果相等，则说明这段期间，没有其他程序对其进行操作，则可以执行更新，将version字段的值加1；如果更新时发现此刻的version值与刚刚获取出来的version的值不相等，则说明这段期间已经有其他程序对其进行操作了，则不进行更新操作。 224 | 225 | **悲观锁** 226 | 227 | - 与乐观锁相对应的就是悲观锁了。悲观锁就是在操作数据时，认为此操作会出现数据冲突，所以在进行每次操作时都要通过获取锁才能进行对相同数据的操作，这点跟java中的synchronized很相似，所以悲观锁需要耗费较多的时间。另外与乐观锁相对应的，悲观锁是由数据库自己实现了的，要用的时候，我们直接调用数据库的相关语句就可以了。 228 | 229 | - 说到这里，由悲观锁涉及到的另外两个锁概念就出来了，它们就是共享锁与排它锁。共享锁和排它锁是悲观锁的不同的实现，它俩都属于悲观锁的范畴。 230 | 231 | > 引自: https://www.cnblogs.com/zousong/p/10513372.html 232 | 233 | ## 14、MySQL 问题排查都有哪些手段？ 234 | 235 | 详情可参考: https://juejin.im/post/5c8375bc5188257fdd0bd252#heading-14 236 | 237 | ## 15、如何做 MySQL 的性能优化？ 238 | 239 | 这个问题太大了,具体可以参考[Mysql高性能优化规范建议](https://www.cnblogs.com/huchong/p/10219318.html)，不过一般对于 MySQL 方面的优化问题,很多时候指的是 SQL 查询很慢之类的问题,对于这类问题怎么分析呢? 240 | 241 | 在业务系统中,除了使用主键进行的查询,其他的我都会在测试库上测试其耗时,慢查询的统计主要由运维在做,会定期将业务中的慢查询反馈给我们. 242 | 243 | 慢查询的优化首先要搞明白慢的原因是什么? 是查询条件没有命中索引?是 load 了不需要的数据列?还是数据量太大? 244 | 245 | 所以优化也是针对这三个方向来的: 246 | 247 | - 首先分析语句,看看是否 load 了额外的数据,可能是查询了多余的行并且抛弃掉了,可能是加载了许多结果中并不需要的列,对语句进行分析以及重写. 248 | - 分析语句的执行计划,然后获得其使用索引的情况,之后修改语句或者修改索引,使得语句可以尽可能的命中索引. 249 | - 如果对语句的优化已经无法进行,可以考虑表中的数据量是否太大,如果是的话可以进行横向或者纵向的分表. 250 | 251 | 如果有时间,推荐看这篇更详细的文章分析 [一条SQL语句执行得很慢的原因有哪些？](https://mp.weixin.qq.com/s?__biz=Mzg2OTA0Njk0OA==&mid=2247485185&idx=1&sn=66ef08b4ab6af5757792223a83fc0d45&chksm=cea248caf9d5c1dc72ec8a281ec16aa3ec3e8066dbb252e27362438a26c33fbe842b0e0adf47&token=79317275&lang=zh_CN#rd) 252 | 253 | > 参考来源:https://mp.weixin.qq.com/s/l9up2dlPniOYO4usoe-dFA 254 | -------------------------------------------------------------------------------- /distributed system/README.md: -------------------------------------------------------------------------------- 1 | # 分布式系统 2 | ## 一、分布式缓存 3 | ### Memcached 4 | - Memcached 简介 5 | - Memcached的分布式算法简介 6 | - Memcached的数据清除算法 7 | - Memcacehd 的工作流程是怎么样的？ 8 | - Memcached 和 Redis 有什么区别？ 9 | - Memcached 适用的业务场景有哪些？ 10 | - Memcached 不适用哪些业务场景？ 11 | - 能够遍历 Memcached 中所有的 item 吗？ 12 | - Memcached 集群是怎么工作的？ 13 | - Memcached 最大的优势是什么？ 14 | - Memcached 和 MySQL 的 query cache 相比，有什么优缺点？ 15 | - Memcached 和服务器的 local cache（比如 PHP 的 APC、mmap 文件等）相比，有什么优缺点？ 16 | - Memcached 的 cache 机制是怎样的？ 17 | - Memcached 如何实现冗余机制？ 18 | - Memcached 如何处理容错的？ 19 | - 如何将 Memcached 中 item 批量导入导出？ 20 | - 如果确实需要把 Memcached 中的 item 批量导出导入，怎么办？ 21 | - Memcached 是如何做身份验证的？ 22 | - Memcached 的多线程是什么？如何使用它们？ 23 | - Memcached 能接受的 key 的最大长度是多少？ 24 | - Memcached 对 item 的过期时间有什么限制？ 25 | - Memcached 最大能存储多大的单个 item？ 26 | - 为什么单个 item 的大小被限制在 1M byte 之内？ 27 | - 可以在不同的 Memcached 节点上使用大小不等的缓存空间吗？如果这么做之后，Memcached 能够更有效地使用内存吗？ 28 | - Memcached 的内存分配器是如何工作的？为什么不适用 malloc/free？为何要使用 slabs？ 29 | - Memcached 是原子的吗？ 30 | - 什么时候失效的数据项会从缓存中删除？ 31 | ### Redis 32 | #### 1、Redis 是什么？都有哪些使用场景？ 33 | 34 | 1、Redis本质上是一个Key-Value类型的内存数据库，很像memcached，整个数据库统统加载在内存当中进行操作，定期通过异步操作把数据库数据flush到硬盘上进行保存。
35 | 2、Redis最适合所有数据in-momory的场景，虽然Redis也提供持久化功能，但实际更多的是一个disk-backed的功能，跟传统意义上的持久化有比较大的差别。 36 | 37 | 那么可能大家就会有疑问，似乎Redis更像一个加强版的Memcached，那么何时使用Memcached，何时使用Redis呢? 38 | 39 | 如果简单地比较Redis与Memcached的区别，大多数都会得到以下观点： 40 | 41 | Redis不仅仅支持简单的k/v类型的数据，同时还提供list，set，zset，hash等数据结构的存储。 42 | Redis支持数据的备份，即master-slave模式的数据备份。 43 | Redis支持数据的持久化，可以将内存中的数据保持在磁盘中，重启的时候可以再次加载进行使用。 44 | 45 | （1）会话缓存（Session Cache） 46 | 47 | 最常用的一种使用Redis的情景是会话缓存（session cache）。 48 | 49 | 用Redis缓存会话比其他存储（如Memcached）的优势在于：Redis提供持久化。当维护一个不是严格要求一致性的缓存时，如果用户的购物车信息全部丢失，大部分人都会不高兴的，现在，他们还会这样吗？ 50 | 51 | 幸运的是，随着 Redis 这些年的改进，很容易找到怎么恰当的使用Redis来缓存会话的文档。甚至广为人知的商业平台Magento也提供Redis的插件。 52 | 53 | （2）全页缓存（FPC） 54 | 55 | 除基本的会话token之外，Redis还提供很简便的FPC平台。回到一致性问题，即使重启了Redis实例，因为有磁盘的持久化，用户也不会看到页面加载速度的下降，这是一个极大改进，类似PHP本地FPC。 56 | 57 | 再次以Magento为例，Magento提供一个插件来使用Redis作为全页缓存后端。 58 | 59 | 此外，对WordPress的用户来说，Pantheon有一个非常好的插件 wp-redis，这个插件能帮助你以最快速度加载你曾浏览过的页面。 60 | 61 | （3）队列 62 | 63 | Reids在内存存储引擎领域的一大优点是提供 list 和 set 操作，这使得Redis能作为一个很好的消息队列平台来使用。Redis作为队列使用的操作，就类似于本地程序语言（如Python）对 list 的 push/pop 操作。 64 | 65 | 如果你快速的在Google中搜索“Redis queues”，你马上就能找到大量的开源项目，这些项目的目的就是利用Redis创建非常好的后端工具，以满足各种队列需求。例如，Celery有一个后台就是使用Redis作为broker，你可以从这里去查看。 66 | 67 | （4）排行榜/计数器 68 | 69 | Redis在内存中对数字进行递增或递减的操作实现的非常好。集合（Set）和有序集合（Sorted Set）也使得我们在执行这些操作的时候变的非常简单，Redis只是正好提供了这两种数据结构。 70 | 71 | 所以，我们要从排序集合中获取到排名最靠前的10个用户–我们称之为“user_scores”。 72 | 73 | 当然，这是假定你是根据你用户的分数做递增的排序。如果你想返回用户及用户的分数，你需要这样执行： 74 | 75 | ```java 76 | ZRANGE user_scores 0 10 WITHSCORES 77 | ``` 78 | Agora Games就是一个很好的例子，用Ruby实现的，它的排行榜就是使用Redis来存储数据的，你可以在这里看到。 79 | 80 | （5）发布/订阅 81 | 82 | 最后（但肯定不是最不重要的）是Redis的发布/订阅功能。 83 | 84 | 发布/订阅的使用场景确实非常多，我已看见人们在社交网络连接中使用，还可作为基于发布/订阅的脚本触发器，甚至用Redis的发布/订阅功能来建立聊天系统！（不，这是真的，你可以去核实）。 85 | 　　 86 | Redis提供的所有特性中，我感觉这个是喜欢的人最少的一个，虽然它为用户提供如此多功能。 87 | #### 2、Redis 有哪些功能？ 88 | 89 | #### 3、Redis 和 memecache 有什么区别？ 90 | - Master写内存快照，save命令调度rdbSave函数，会阻塞主线程的工作，当快照比较大时对性能影响是非常大的，会间断性暂停服务，所以Master最好不要写内存快照。 91 | - Master AOF持久化，如果不重写AOF文件，这个持久化方式对性能的影响是最小的，但是AOF文件会不断增大，AOF文件过大会影响Master重启的恢复速度。 92 | Master最好不要做任何持久化工作，包括内存快照和AOF日志文件，特别是不要启用内存快照做持久化，如果数据比较关键，某个Slave开启AOF备份数据，策略为每秒同步一次。 93 | - Master调用BGREWRITEAOF重写AOF文件，AOF在重写的时候会占大量的CPU和内存资源，导致服务load过高，出现短暂服务暂停现象。 94 | - Redis主从复制的性能问题，为了主从复制的速度和连接的稳定性，Slave和Master最好在同一个局域网内。 95 | 96 | #### 4、Redis 为什么是单线程的？ 97 | #### 5、什么是缓存穿透？怎么解决？ 98 | #### 6、Redis 支持的数据类型有哪些？ 99 | - String、List、Set、Sorted Set、hash。 100 | #### 7、Redis 支持的 java 客户端都有哪些？ 101 | - Redisson、Jedis、lettuce等等，官方推荐使用Redisson。 102 | #### 8、Jedis 和 redisson 有哪些区别？ 103 | - Jedis是Redis的Java实现的客户端，其API提供了比较全面的Redis命令的支持； 104 | - Redisson实现了分布式和可扩展的Java数据结构，和Jedis相比，功能较为简单，不支持字符串操作，不支持排序、事务、管道、分区等Redis特性； - Redisson的宗旨是促进使用者对Redis的关注分离，从而让使用者能够将精力更集中地放在处理业务逻辑上。 105 | #### 9、怎么保证缓存和数据库数据的一致性？ 106 | #### 10、Redis 持久化有几种方式？ 107 | - 1、快照（snapshots） 108 | 109 | 缺省情况情况下，Redis把数据快照存放在磁盘上的二进制文件中，文件名为dump。rdb。你可以配置Redis的持久化策略，例如数据集中每N秒钟有超过M次更新，就将数据写入磁盘；或者你可以手工调用命令SAVE或BGSAVE。 110 | 111 | **工作原理** 112 | 113 | - Redis forks。 114 | - 子进程开始将数据写到临时RDB文件中。 115 | - 当子进程完成写RDB文件，用新文件替换老文件。 116 | - 这种方式可以使Redis使用copy-on-write技术。 117 | - 2、AOF 118 | 119 | 快照模式并不十分健壮，当系统停止，或者无意中Redis被kill掉，最后写入Redis的数据就会丢失。这对某些应用也许不是大问题，但对于要求高可靠性的应用来说，Redis就不是一个合适的选择。 120 | 121 | Append-only文件模式是另一种选择。你可以在配置文件中打开AOF模式。 122 | 123 | - 3、虚拟内存方式 124 | 125 | 当你的key很小而value很大时，使用VM的效果会比较好。因为这样节约的内存比较大。当你的key不小时，可以考虑使用一些非常方法将很大的key变成很大的value，比如你可以考虑将key，value组合成一个新的value。 126 | 　　 127 | vm-max-threads这个参数，可以设置访问swap文件的线程数，设置最好不要超过机器的核数，如果设置为0，那么所有对swap文件的操作都是串行的。可能会造成比较长时间的延迟，但是对数据完整性有很好的保证。 128 | 129 | 自己测试的时候发现用虚拟内存性能也不错。如果数据量很大，可以考虑分布式或者其他数据库 130 | #### 11、Redis 怎么实现分布式锁？ 131 | #### 12、Redis 分布式锁有什么缺陷？ 132 | #### 13、Redis 如何做内存优化？ 133 | #### 14、Redis 淘汰策略有哪些？ 134 | #### 15Redis 常见的性能问题有哪些？该如何解决？ 135 | 136 | > 整理来源： 137 | 1、https://mp.weixin.qq.com/s/HMHTEv9WGgTDPtd-iaiEOA 138 | 2、https://juejin.im/post/5cb13b4d6fb9a0687b7dd0bd#heading-42 139 | 140 | 141 | ## 二、分布式服务框架 142 | ### Dubbo 143 | - Dubbo简介 144 | - 待续 145 | 146 | ## 三、分布式协调服务 147 | ### Zookeeper 148 | - 简述Zookeeper 149 | - 简述ZAB协议 150 | - 简述Paxos算法 151 | - ZK如何保证数据的一致性？ 152 | - Dubbo简介及以Zookeeper为注册中心 153 | - Zookeeper的leader选举过程 154 | - 2PC and 3PC 155 | - 简述Zookeeper的watcher 156 | - 简述ZAB集群数据同步的过程 157 | - 简述Zookeeper中的ACL 158 | - Zookeeper底层是如何实现数据一致性的？ 159 | - Zookeeper在yarn框架中如何实现避免脑裂的? 160 | 161 | ## 四、分布式消息队列 162 | ### RabbitMQ 163 | - 什么是RabbitMQ? 164 | - 为什么要使用RabbitMQ? 165 | - 消息队列的优缺点？ 166 | - RabbitMQ 与 Kafka 有什么区别？ 167 | - RabbitMQ 的使用场景有哪些？ 168 | - RabbitMQ 有哪些重要的角色？ 169 | - RabbitMQ 有哪些重要的组件？ 170 | - RabbitMQ 中 vhost 的作用是什么？ 171 | - RabbitMQ 的消息是怎么发送的？ 172 | - RabbitMQ 怎么保证消息的稳定性？ 173 | - RabbitMQ 怎么避免消息丢失？ 174 | - 要保证消息持久化成功的条件有哪些？ 175 | - RabbitMQ 持久化有什么缺点？ 176 | - RabbitMQ 有几种广播类型？ 177 | - RabbitMQ 怎么实现延迟消息队列？ 178 | - RabbitMQ 集群有什么用？ 179 | - RabbitMQ 节点的类型有哪些？ 180 | - RabbitMQ 集群搭建需要注意哪些问题？ 181 | - RabbitMQ 每个节点是其他节点的完整拷贝吗？为什么？ 182 | - RabbitMQ 集群中唯一一个磁盘节点崩溃了会发生什么情况？ 183 | - RabbitMQ 对集群节点停止顺序有要求吗？ 184 | ### Kafka 185 | - Kafka 都有哪些特点？ 186 | - 请简述下你在哪些场景下会选择 Kafka？ 187 | - 简述Kafka 的设计架构 188 | - Kafka 分区的目的 189 | - Kafka 是如何做到消息的有序性的？ 190 | - Kafka 的高可靠性是怎么实现的？ 191 | - 请谈一谈 Kafka 数据一致性原理 192 | - ISR、OSR、AR 是什么？ 193 | - LEO、HW、LSO、LW等分别代表什么 194 | - Kafka 在什么情况下会出现消息丢失？ 195 | - 怎么尽可能保证 Kafka 的可靠性 196 | - 消费者和消费者组有什么关系？ 197 | - Kafka 的每个分区只能被一个消费者线程，如何做到多个线程同时消费一个分区？ 198 | - 数据传输的事务有几种？ 199 | - Kafka 消费者是否可以消费指定分区消息？ 200 | - Kafka消息是采用Pull模式，还是Push模式？ 201 | - 如何为Kafka集群选择合适的Topics/Partitions数量 202 | - 待续 203 | 204 | ## 五、分布式搜索引擎 205 | 206 | ### Elasticsearch 207 | - Elasticsearch简介 208 | 209 | ### Solr 210 | ![Solr](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/Solr.png) 211 | - [1、Solr简介](https://github.com/bigrotor187/awesome-java-interview/blob/master/distributed%20system/README.md#1solr%E7%AE%80%E4%BB%8B) 212 | - [2、简述Solr的倒排索引](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#2%E7%AE%80%E8%BF%B0solr%E7%9A%84%E5%80%92%E6%8E%92%E7%B4%A2%E5%BC%95) 213 | - [3、为什么要使用Solr?](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#3%E4%B8%BA%E4%BB%80%E4%B9%88%E8%A6%81%E4%BD%BF%E7%94%A8solr) 214 | - [4、Solr和elasticsearch的区别？](https://github.com/bigrotor187/awesome-java-interview/tree/master/distributed%20system#4solr%E5%92%8Celasticsearch%E7%9A%84%E5%8C%BA%E5%88%AB) 215 | 216 | #### 1、Solr简介 217 | - Solr 是一个 Java 开发的基于 Lucene 的`企业级`、`开源`、`全文搜索`平台。它采用的是`反向索引`，即从关键字到文档的映射过程。 218 | - Solr 的资源`Document`为对象进行存储，每个文档由一系列的`Field`构成，每个`Field`表示资源的一个属性。 文档的`Field`可以被索引，以提供高性能的搜索效率。 一般情况下文档都包含一个能唯一表示该文档的id字段。 219 | 220 | #### 2、简述Solr的倒排索引 221 | - 倒排索引就是从文档内容到文档序号的过程，将文档内容用solr自带分词器进行分词，然后作为索引，用二分法将关键字与排序号的索引进行匹配，进而查找到对应文档。 222 | 223 | > 【注】可参考：1、https://blog.csdn.net/chunlei_zhang/article/details/38520315
224 | 2、https://blog.csdn.net/hu948162999/article/details/42463043 225 | #### 3、为什么要使用Solr? 226 | - Solr 是一个 Java 开发的基于 Lucene 的`企业级`、`开源`、`全文搜索`平台，严格来说，Lucene 负责数据存储，而 Solr 作为一个引擎提供搜索和插入功能，跟数据库的解释器是一样的。但是，如果数据库中有一个字段存了很长的文本，比如存了 1000 个汉字，现在想要从中搜一个词的时候，普通的数据库会使用 like 去查询，遍历整个文本去模糊匹配，效率很低。 227 | - 所以，为了解决这个问题，自然而然地使用全文搜索工具是最好地。比如 lucene 所作的就是分词，然后去匹配分词的词中是否有想搜的词即可。而 Solr 正是基于 Lucene 实现的，使用 Solr 的检索功能可以大大提高检索效率。 228 | #### 4、Solr和elasticsearch的区别？ 229 | - 共同点： 230 | - solr 和 elasticsearch 都是基于 Lucene 实现的。 231 | - 不同点： 232 | - 1、solr 利用 zookeeper 进行分布式管理，而 elasticsearch 自身带有分布式协调管理功能； 233 | - 2、solr 比 elasticsearch 实现更加全面，solr 官方提供的功能更多，而 elasticsearch 本身更注 重于核心功能，高级功能多由第三方插件提供； 234 | - 3、solr 在传统的搜索应用中表现好于 elasticsearch，而 elasticsearch 在实时搜索应用方面比 solr 表现好。 235 | - 最后有必要说明一下传统搜索和实时搜索： 236 | - 传统搜索是从静态数据库中筛选出符合条件的结果，这种结果往往是不可变得、静态的。而实时搜索则是说用户对于搜索的结果是实时变化的。 237 | - 传统搜索比如电商这种，实时搜索参考谷歌，百度，这种实时搜索。 238 | 239 | ## 六、分布式事务 240 | - 刚性分布式事务 241 | - 柔性分布式事务 242 | - 两阶段提交协议&三阶段提交协议 243 | - 一致性哈希算法 244 | -------------------------------------------------------------------------------- /framework/README.md: -------------------------------------------------------------------------------- 1 | |[Spring](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#spring)|[SpringMVC](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#springmvc)|[Mybatis](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#mybatis)|[SpringBoot](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#springboot)|[Hibernate](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#hibernate)|[Redis](https://github.com/bigrotor187/awesome-java-interview/tree/master/framework#redis)| 2 | |------|---------|-------|----------|---------|------| 3 | 4 | # Spring 5 | 6 | ## Spring Framework 7 | 8 | - [1、Spring 是如何简化 Java 开发的？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#1spring-%E6%98%AF%E5%A6%82%E4%BD%95%E7%AE%80%E5%8C%96-java-%E5%BC%80%E5%8F%91%E7%9A%84) 9 | - [2、什么是 Spring Framework？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#2%E4%BB%80%E4%B9%88%E6%98%AF-spring-framework) 10 | - [3、Spring Framework 有哪些优点？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#3spring-framework-%E6%9C%89%E5%93%AA%E4%BA%9B%E4%BC%98%E7%82%B9) 11 | - [4、Spring 有哪些子项目吗？请简要描述。](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#4spring-%E6%9C%89%E5%93%AA%E4%BA%9B%E5%AD%90%E9%A1%B9%E7%9B%AE%E5%90%97%E8%AF%B7%E7%AE%80%E8%A6%81%E6%8F%8F%E8%BF%B0) 12 | - [5、Spring 框架中用到了哪些设计模式？请举例说明。](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#5spring-%E6%A1%86%E6%9E%B6%E4%B8%AD%E7%94%A8%E5%88%B0%E4%BA%86%E5%93%AA%E4%BA%9B%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F%E8%AF%B7%E4%B8%BE%E4%BE%8B%E8%AF%B4%E6%98%8E) 13 | - [6、Spring 有哪些最佳实践？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#6spring-%E6%9C%89%E5%93%AA%E4%BA%9B%E6%9C%80%E4%BD%B3%E5%AE%9E%E8%B7%B5) 14 | 15 | ### **1、Spring 是如何简化 Java 开发的？** 16 | 17 | 为了降低 Java 开发的复杂性，Spring 采取了以下 4 种关键策略： 18 | - 基于 POJO 的轻量级和最小侵入性编程； 19 | - 通过依赖注入和面向接口实现松耦合； 20 | - 基于切面和惯例进行声明式编程； 21 | - 通过切面和模板减少样板式代码。 22 | 23 | ### **2、什么是 Spring Framework？** 24 | 25 | Spring 是一个开源框架，Spring 诞生之初的主要目的是作为 EJB 的轻量级替代品，旨在降低应用程序开发的复杂度。它增强了 POJO，使之具备了之前只有 EJB 和其他企业级 Java 规范才具有的功能。 26 | - Spring 是轻量级、松散耦合的。 27 | > 它的轻量级主要是相对于 EJB 而言。但是随着 Spring 体系越来越庞大，添加 Spring 的依赖管理越来越耗时，写配置挤占了写应用程序逻辑的时间，所以后来推出了 Spring Boot。 28 | - Spring 具有分层体系结构，允许用户选择组件，同时为 J2EE 应用程序开发提供了一个有凝聚力的框架。 29 | - Spring 可以继承其他框架，如 Spring MVC、Hibernate、Mybatis 等，所以又被称为框架饿的框架（粘合剂、脚手架） 30 | 31 | ### **3、Spring Framework 有哪些优点？** 32 | - 轻量级：在开发中使用框架会有一点点开销，但不会像重量级的 EJB 一样 33 | - 控制反转（IOC）：也叫依赖注入，Spring 容器负责处理各种对象的依赖关系，而不是创建或查找依赖对象 34 | - 面向切面编程（AOP）：Spring 支持 AOP 将业务逻辑与系统服务分开 35 | - IOC 容器：它管理 Spring Bean 生命周期和项目特定配置 36 | - MCV 框架（Spring Mvc）：用于创建 Web 应用程序或 RESTful Web 服务，能够返回 XML / JSON 响应 37 | - 事务管理：通过使用 Java 注解或 Spring Bean XML 配置文件，减少 JDBC　操作和文件上传等的样板代码量，适程序更加简洁 38 | - 异常处理：Spring 提供了一个方便的 API，用于将特定技术的异常转换为非检查型的异常 39 | 40 | ### **4、Spring 有哪些子项目吗？请简要描述。** 41 | - Core：提供 Spring 框架核心基础部分的关键模块，比如 Ioc 或 DI 42 | - JDBC：此模块启用 JDBC 抽象层，无需对特定供应商数据库执行 JDBC 编码 43 | - ORM 集成：为流行的对象映射 API 提供集成，例如 JPA、JDO、Hibernate、Mybatis 等 44 | - Web：面向 Web 的集成模块，提供多部分文件上载，Servlet 监听器和面向 Web 的应用程序上下文功能 45 | - MVC framework：一个实现了模型-视图-控制设计模式的 Web 模块 46 | - AOP 模块：面向切面编程的实现允许定义更加简洁的方法-拦截器和切入点 47 | 48 | ![](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/Spring%E7%BB%84%E4%BB%B6.png) 49 | 50 | ### **5、Spring 框架中用到了哪些设计模式？请举例说明。** 51 | 52 | - 代理模式（Proxy Pattern） — 在 AOP 和 remoting 中被用的比较多。 53 | - 单例模式（Singleton Pattern） — 在 Spring 配置文件中定义的 Bean 默认为单例模式。 54 | - 模板方法（Template Method Pattern） —用来解决代码重复的问题。如 RestTemplate、JmsTemplate、JdbcTemplate 。 55 | - 前端控制器（Front Controller） — Spring提供了 DispatcherServlet 来对请求进行分发。 56 | - 视图帮助(View Helper) — Spring 提供了一系列的 JSP 标签，高效宏来辅助将分散的代码整合在视图里。 57 | - 依赖注入（Dependency Injection） — 贯穿于 BeanFactory / ApplicationContext 接口的核心理念。 58 | - 工厂模式（Factory Pattern） — BeanFactory 用来创建对象的实例。 59 | - 适配器模式（Adapter Pattern） — 主要在 Spring Web 和 Spring MVC 模块应用。 60 |
61 | 62 | > 更多详情请参考:
63 | （1）[Spring 框架中的设计模式（一）](http://www.iocoder.cn/Spring/DesignPattern-1/)
64 | （2）[Spring 框架中的设计模式（二）](http://www.iocoder.cn/Spring/DesignPattern-2/)
65 | （3）[Spring 框架中的设计模式（三）](http://www.iocoder.cn/Spring/DesignPattern-3/)
66 | （4）[Spring 框架中的设计模式（四）](http://www.iocoder.cn/Spring/DesignPattern-4/)
67 | （5）[Spring 框架中的设计模式（五）](http://www.iocoder.cn/Spring/DesignPattern-5/) 68 | 69 | ### **6、Spring 有哪些最佳实践？** 70 | 71 | - 为组件使用正确的注解可以一目了然当前层的作用。比如，对于控制层，使用 @Controller，对于业务层，使用 @Service， 对于 DAO 层使用 @Repository。 72 | - 可以根据具体用途划分 Spring Bean，如 spring-jdbc.xml, spring-security.xml 等。 73 | - 尽可能地配置 bean 依赖项，尽量避免自动装配。 74 | - 对于应用程序级的属性，最好的方法是创建属性文件并在 Spring Bean 的配置文件中读取它。 75 |
76 | 77 | > 更多详情请参考：[spring-best-practices](https://www.journaldev.com/2696/spring-interview-questions-and-answers#spring-best-practices) 78 | 79 | 80 | ## Spring Bean 81 | - [1、什么是 Spring Bean？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#1%E4%BB%80%E4%B9%88%E6%98%AF-spring-bean) 82 | - [2、Spring Bean 配置文件的重要性是什么？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#2spring-bean-%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E7%9A%84%E9%87%8D%E8%A6%81%E6%80%A7%E6%98%AF%E4%BB%80%E4%B9%88) 83 | - [3、Spring Bean 有哪些配置方式？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#3spring-bean-%E6%9C%89%E5%93%AA%E4%BA%9B%E9%85%8D%E7%BD%AE%E6%96%B9%E5%BC%8F) 84 | - [4、Spring Bean 支持哪几种 Bean Scope？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#4spring-bean-%E6%94%AF%E6%8C%81%E5%93%AA%E5%87%A0%E7%A7%8D-bean-scope) 85 | - [5、Spring Bean 的生命周期是什么样的？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#5spring-bean-%E7%9A%84%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F%E6%98%AF%E4%BB%80%E4%B9%88%E6%A0%B7%E7%9A%84) 86 | - [6、Spring 中单例 Bean 是线程安全的吗？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#6spring-%E4%B8%AD%E5%8D%95%E4%BE%8B-bean-%E6%98%AF%E7%BA%BF%E7%A8%8B%E5%AE%89%E5%85%A8%E7%9A%84%E5%90%97) 87 | - [7、Spring Bean 是否提供线程安全性？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#7spring-bean-%E6%98%AF%E5%90%A6%E6%8F%90%E4%BE%9B%E7%BA%BF%E7%A8%8B%E5%AE%89%E5%85%A8%E6%80%A7) 88 | - [8、Spring 有哪些依赖注入的方式？或者说 Spring 是如何注入 bean 的？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#8spring-%E6%9C%89%E5%93%AA%E4%BA%9B%E4%BE%9D%E8%B5%96%E6%B3%A8%E5%85%A5%E7%9A%84%E6%96%B9%E5%BC%8F%E6%88%96%E8%80%85%E8%AF%B4-spring-%E6%98%AF%E5%A6%82%E4%BD%95%E6%B3%A8%E5%85%A5-bean-%E7%9A%84) 89 | - [9、Spring Bean 定义是如何生成的？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#9spring-bean-%E5%AE%9A%E4%B9%89%E6%98%AF%E5%A6%82%E4%BD%95%E7%94%9F%E6%88%90%E7%9A%84) 90 | - [10、Spring Bean 定义是如何注册的？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#10spring-bean-%E5%AE%9A%E4%B9%89%E6%98%AF%E5%A6%82%E4%BD%95%E6%B3%A8%E5%86%8C%E7%9A%84) 91 | 92 | ### **1、什么是 Spring Bean？** 93 | - Spring Bean 是由 Spring IoC 容器初始化的 Java 对象。 94 | - Spring Bean 由 Spring IoC 容器实例化，配置，装配和管理。 95 | - Spring Bean 基于用户提供给 IoC 容器的配置元数据 Bean Definition 创建。 96 | 97 | ### **2、Spring Bean 配置文件的重要性是什么？** 98 | - 当使用 Spring Bean 配置文件来定义将由 Spring Context 初始化的所有 Bean 时，在创建 Spring ApplicationContext 实例时，会去读取 spring bean XML 配置文件并初始化这些文件 99 | - 初始化上下文后，可以通过它获取不同的 Bean 实例 100 | - 除了 Spring Bean 的配置之外，该文件还包含 Spring MVC 拦截器，视图解析器以及其他元素，以支持基于注解的配置 101 | 102 | ### **3、Spring Bean 有哪些配置方式？** 103 | - XML 配置 104 | - Java Config 配置 105 | - 注解配置 106 | ### **4、Spring Bean 支持哪几种 Bean Scope？** 107 | - Singleton 108 | - Prototype 109 | - Request 110 | - Session 111 | - Application 112 | ### **5、Spring Bean 的生命周期是什么样的？** 113 | - 首先，需要基于Java或XML bean定义来实例化Spring bean。可能还需要执行一些初始化以使其进入可用状态。 114 | - 之后，当不再需要bean时，它将从IoC容器中删除。 115 | 116 | ![Spring组件](https://github.com/bigrotor187/awesome-java-interview/blob/master/img/Spring%20Framework.jpg) 117 | 118 | ### **6、Spring 中单例 Bean 是线程安全的吗？** 119 | - Spring 中单例 Bean 不是线程安全的，因为线程安全是关于执行的，而单例则是一种专注于创建的设计模式 120 | - 线程安全仅仅取决于 bean 本身的实现 121 | - Spring 使用 ThreadLocal 解决线程安全问题，“以空间换时间”的方式为每一个线程都提供了一份变量，因此可以同时访问而互不影响。 122 | > 更多详情请参考：
123 | > （1）[Spring单例与线程安全小结](https://www.cnblogs.com/doit8791/p/4093808.html)
124 | > （2）[聊一聊Spring中的线程安全性](https://juejin.im/post/5a0045ef5188254de169968e#heading-0) 125 | 126 | ### **7、Spring Bean 是否提供线程安全性？** 127 | 128 | - Spring 并没有保证对象的线程安全，需要由开发者自己编写解决线程安全问题的代码。 129 | - Spring 对每个 bean 提供了一个 scope 属性来表示该 bean 的作用域，其中默认的 scope 是 singleton，因此每个上下文只有一个实例。这意味所有线程都共享一个单例实例 Bean，因此存在资源竞争，可能会导致数据不一致。因此，在默认模式下，spring bean不是线程安全的。 130 | - 可以将 Spring Bean 的 scope 从 singleton 修改为 request, prototype or session 来获得线程安全，但是会牺牲一部分性能。 131 | 132 | ### **8、Spring 有哪些依赖注入的方式？或者说 Spring 是如何注入 bean 的？** 133 | 134 | - setter注入 135 | - 构造器注入 136 | - 接口注入 137 | 138 | 139 | ### **9、Spring Bean 定义是如何生成的？** 140 | - bean 定义表示对一个类的描述，所以要先生成 bean 定义，然后把它注册到容器中。 141 | - bean 定义的生成主要有两种方式，一种是基于类本身，如知道了类名或类的 class。还有一种是不知道类本身的信息，但是知道它是由一个其他类的工厂方法返回的。而工厂方法又分为静态的和非静态的，所以我们只能记录下这些工厂方法信息到 bean 定义中，在运行时调用工厂方法，获取 bean 的实例对象。 142 | - 工厂方法这种应用场景不多，所以实际上很少用。 143 | 144 | ### **10、Spring Bean 定义是如何注册的？** 145 | - 使用注解注册 bean 定义 146 | - 标有 @Component 注解的类 147 | - 标有 @Configuration 注解的类 148 | - 标有 @Configuration 注解的类里标有 @Bean 注解的方法返回的类 149 | 150 | > PS：这种方式可以用于业务类的注册，也可以用于 Spring 框架内部的类注册。优点是简单方便，缺点是不够灵活，很难根据一个条件判断来注册不同的 bean 定义。 151 | - 使用 XML 配置注册 bean 定义 152 | - 在标有 @Configuration 注解的类上，使用 @ImportResource 注解引入 XML 配置文件 153 | 154 | > PS：这种方式是在注解里也能使用 XML。建议是尽量不用，优先使用注解的方式，除非是是在历史遗留的系统中。 155 | 156 | - 使用 @Import 注解引入 157 | - 在标有 @Configuration 注解的类上，使用 @Import 注解引入其他标有 @Configuration 注解的类 158 | 159 | > PS：这种方式仅用于没有类路径扫描功能的代码，现在大都基于 SpringBoot，所以这种方式现在很少用了。 160 | 161 | - 使用 ImportSelector 接口注册 bean 定义 162 | ```java 163 | public interface ImportSelector { 164 | String[] selectImports(AnnotationMetadata importingClassMetadata); 165 | } 166 | ``` 167 | 168 | > PS：
169 | （1）接口方法返回的是类名称的数组，这些类将会被注册 bean 定义。
170 | （2）在实现这个接口时，可以根据不同的情况返回不同的类名称，这就非常的灵活，实现了动态注册 bean 定义的需求。 171 | 172 | - 使用 ImportBeanDefinitionRegistrar 接口注册 bean 定义 173 | ```java 174 | public interface ImportBeanDefinitionRegistrar { 175 | void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry); 176 | } 177 | ``` 178 | 179 | > PS：这个接口没有返回值，所以需要自己写代码直接注册 bean 定义，当然也是非常灵活的。在用法上和上面方法一样，包括接口方法参数的含义也一样。 180 | 181 | - 使用 BeanDefinitionRegistryPostProcessor 接口注册 bean 定义 182 | 183 | ```java 184 | public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor { 185 | void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeanException; 186 | } 187 | ``` 188 | 189 | > PS：
190 | （1）`BeanDefinitionRegistryPostProcessor`接口专门为其他类注册 `bean` 定义，通过 `postProcessBeanDefinitionRegistry` 方法来实现；
191 | （2）`BeanDefinitionRegistryPostProcessor`接口有一个非常重要的实现类 `ConfigurationClassPostProcessor`，里面包含了所有 Spring 支持的注册 `bean` 定义方式的实现。
192 | （3）Spring 统一了编程模型，所以 `ConfigurationClassPostProcessor` 类也被注册了 `bean` 定义。 193 | 194 | 更多详情请参考：[品Spring：bean定义上梁山](https://mp.weixin.qq.com/s/FDtjJrPMgciM_W7vUpNVbg) 195 | 196 | ## Spring IoC 197 | 198 | - **[1、什么是 Spring IoC 框架？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#3ioc-%E5%92%8C-di-%E6%9C%89%E4%BB%80%E4%B9%88%E5%8C%BA%E5%88%AB)** 199 | - **[2、什么是依赖注入？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#2%E4%BB%80%E4%B9%88%E6%98%AF%E4%BE%9D%E8%B5%96%E6%B3%A8%E5%85%A5)** 200 | - **[3、IoC 和 DI 有什么区别？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#3ioc-%E5%92%8C-di-%E6%9C%89%E4%BB%80%E4%B9%88%E5%8C%BA%E5%88%AB)** 201 | - **[4、Spring 中有哪几种容器？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#4spring-%E4%B8%AD%E6%9C%89%E5%93%AA%E5%87%A0%E7%A7%8D%E5%AE%B9%E5%99%A8)** 202 | - **[5、Spring 有哪些常用的 BeanFactory 容器？请简要介绍一下。](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#5spring-%E6%9C%89%E5%93%AA%E4%BA%9B%E5%B8%B8%E7%94%A8%E7%9A%84-beanfactory-%E5%AE%B9%E5%99%A8%E8%AF%B7%E7%AE%80%E8%A6%81%E4%BB%8B%E7%BB%8D%E4%B8%80%E4%B8%8B)** 203 | - **[6、Spring 有哪些常用的 ApplicationContext 容器？请简要介绍一下。](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#6spring-%E6%9C%89%E5%93%AA%E4%BA%9B%E5%B8%B8%E7%94%A8%E7%9A%84-applicationcontext-%E5%AE%B9%E5%99%A8%E8%AF%B7%E7%AE%80%E8%A6%81%E4%BB%8B%E7%BB%8D%E4%B8%80%E4%B8%8B)** 204 | - **[7、Spring IoC 有什么好处/优点？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#7spring-ioc-%E6%9C%89%E4%BB%80%E4%B9%88%E5%A5%BD%E5%A4%84%E4%BC%98%E7%82%B9)** 205 | - **[8、请简述 Spring IoC 的实现机制。](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#8%E8%AF%B7%E7%AE%80%E8%BF%B0-spring-ioc-%E7%9A%84%E5%AE%9E%E7%8E%B0%E6%9C%BA%E5%88%B6)** 206 | - **[9、Spring IoC 中有哪些不同类型的事件？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#9spring-ioc-%E4%B8%AD%E6%9C%89%E5%93%AA%E4%BA%9B%E4%B8%8D%E5%90%8C%E7%B1%BB%E5%9E%8B%E7%9A%84%E4%BA%8B%E4%BB%B6)** 207 | - **[10、Spring 中哪种注入 bean 的方式是最好的？为什么？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#10spring-%E4%B8%AD%E5%93%AA%E7%A7%8D%E6%B3%A8%E5%85%A5-bean-%E7%9A%84%E6%96%B9%E5%BC%8F%E6%98%AF%E6%9C%80%E5%A5%BD%E7%9A%84%E4%B8%BA%E4%BB%80%E4%B9%88)** 208 | - **[11、BeanFactory 和 Application 两种容器有什么区别？](https://github.com/bigrotor187/awesome-java-interview/blob/master/framework/README.md#11beanfactory-%E5%92%8C-application-%E4%B8%A4%E7%A7%8D%E5%AE%B9%E5%99%A8%E6%9C%89%E4%BB%80%E4%B9%88%E5%8C%BA%E5%88%AB)** 209 | 210 | ### **1、什么是 Spring IoC 框架？** 211 | 212 | Spring 框架的核心是 Spring IoC 容器，容器通过创建 Bean 对象，将它们装配在一起并配置和管理这些对象的整个生命周期。 213 | - Spring 容器使用**依赖注入**来管理组成应用程序的 Bean 对象。 214 | - 容器通过读取提供的**配置元数据（configuration metadata）**的 Bean Definition 来接收对象进行实例化，配置和组装的指令。 215 | - 该配置元数据的 Bean Definition 可以通过 XML，Java 注解或 Java Config 代码来**提供*。 216 | 217 | ### **2、什么是依赖注入？** 218 | 219 | - 依赖注入是控制反转（IoC）的一个方面，是一个通用概念，表明我们不需要手动创建对象，而是描述应如何创建它们。如果需要，IoC 容器将实例化所需的类。 220 | - 不需要直接在代码中将组件和服务连接在一起，而是描述配置文件中哪些组件需要哪些服务。然后，再由 IoC 容器将它们装配在一起。 221 | 222 | ### **3、IoC 和 DI 有什么区别？** 223 | 224 | - IoC 是目的，DI 是手段,IoC 是指让生成类的方式由传统方式（new）反过来，既程序员不调用 new,需要类的时候由框架注入（DI），是对同一事件不同层面的解读。 225 | 226 | ### **4、Spring 中有哪几种容器？** 227 | 228 | Spring 提供了两种最容器，分别是 `BeanFactory` 和 `ApplicationContext`。 229 | - BeanFactory 230 | - BeanFactory 在 spring-beans 项目中提供，默认会使用懒加载的方式来进行 Bean 对象的初始化。 231 | - Beanfactory 就像是一个生产 Bean 的工厂，BeanFactory API 为 Spring 的 IoC 功能提供了基础,实际上Beanfactory只是一个接口，定义了最基本的方法，它会在客户端要求实例化 Bean 对象。 232 | - ApplicationContext 233 | - ApplicationContext 在 spring-context 项目中提供，并且继承自 BeanFactory 接口，扩展了BeanFactory 接口，在 BeanFactory 基础上提供了国际化等许多高级的扩展实现。默认情况下会自动初始化那些非懒加载的 bean 对象。其内置的一些功能如下： 234 | - MessageSource ：管理 message ，实现国际化等功能。 235 | - ApplicationEventPublisher ：事件发布。 236 | - ResourcePatternResolver ：多资源加载。 237 | - EnvironmentCapable ：系统 Environment（profile + Properties）相关。 238 | - Lifecycle ：管理生命周期。 239 | - Closable ：关闭，释放资源 240 | - InitializingBean：自定义初始化。 241 | - BeanNameAware：设置 beanName 的 Aware 接口。 242 | 243 | ### **5、Spring 有哪些常用的 BeanFactory 容器？请简要介绍一下。** 244 | - BeanFactory 容器中最常用的是 XmlBeanFactory 。它可以根据 XML 文件中定义的内容，创建相应的 Bean。 245 | ### **6、Spring 有哪些常用的 ApplicationContext 容器？请简要介绍一下。** 246 | - ApplicationContext 容器中最常用的主要有以下几种实现： 247 | - ClassPathXmlApplicationContext ：从 ClassPath 的 XML 配置文件中读取上下文，并生成上下文定义。应用程序上下文从程序环境变量中取得。 248 | ```java 249 | ApplicationContext context = new ClassPathXmlApplicationContext(“bean.xml”); 250 | ``` 251 | - FileSystemXmlApplicationContext ：由文件系统中的XML配置文件读取上下文。 252 | ```java 253 | ApplicationContext context = new FileSystemXmlApplicationContext(“bean.xml”); 254 | ``` 255 | - XmlWebApplicationContext ：由 Web 应用的XML文件读取上下文。例如在 Spring MVC 中使用的情况。 256 | - Spring Boot 中，使用的是 ApplicationContext 容器中的 ConfigServletWebServerApplicationContext。 257 | ### **7、Spring IoC 有什么好处/优点？** 258 | ### **8、请简述 Spring IoC 的实现机制。** 259 | ### **9、Spring IoC 中有哪些不同类型的事件？** 260 | ### **10、Spring 中哪种注入 bean 的方式是最好的？为什么？** 261 | ### **11、BeanFactory 和 Application 两种容器有什么区别？** 262 | - BeanFactory 提供容器的接口，提供并管理 bean 实例 263 | - ApplicationContext 提供容器的接口，容纳应用程序中的所有信息，元数据和 bean ，同时它还扩展了 BeanFactory 接口 264 | 265 | 266 | 267 | ## Spring 注解 268 | 269 | ### **1、什么是基于注解的容器配置？** 270 | ### **2、@Component、@Controller、@Repository、@Service 之间有什么区别？** 271 | ### **3、@RequestMapping 注解是如何工作的？** 272 | ### **4、@Required 注解有什么用？** 273 | ### **5、@Autowired 注解有什么用？** 274 | ### **6、@Qualifier 注解有什么而用？** 275 | 276 | ## Spring AOP 277 | 278 | 279 | 280 | ## Spring 事务 281 | 282 | 283 | 284 | # SpringMVC 285 | 286 | # Mybatis 287 | 288 | # SpringBoot 289 | 290 | # Hibernate 291 | 292 | # Redis 293 | -------------------------------------------------------------------------------- /img/MySQL命令行查看版本号.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/MySQL命令行查看版本号.jpg -------------------------------------------------------------------------------- /img/README.md: -------------------------------------------------------------------------------- 1 | 2 | -------------------------------------------------------------------------------- /img/Solr.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/Solr.png -------------------------------------------------------------------------------- /img/Spring Framework.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/Spring Framework.jpg -------------------------------------------------------------------------------- /img/Spring组件.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/Spring组件.png -------------------------------------------------------------------------------- /img/status查看版本号.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/status查看版本号.jpg -------------------------------------------------------------------------------- /img/系统函数查看版本号.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/bigrotor187/fucking-java-interview/7633eba6b88fad52a0d26860fb85a7974fff7633/img/系统函数查看版本号.jpg --------------------------------------------------------------------------------