├── .github └── workflows │ └── maven.yml ├── .gitignore ├── .mvn └── wrapper │ ├── maven-wrapper.jar │ └── maven-wrapper.properties ├── LICENSE ├── README.md ├── mvnw ├── mvnw.cmd ├── pom.xml └── src ├── main └── java │ └── com │ └── di │ └── framework │ ├── OwnDi.java │ ├── OwnDiFramework.java │ ├── annotation │ └── OwnInject.java │ └── module │ ├── IModule.java │ └── impl │ └── AbstractModule.java └── test └── java └── com └── di └── framework ├── OwnDiFrameworkTest.java └── example ├── ConstructorInjectionExample.java ├── FieldInjectionExample.java └── service ├── CalculatorService.java ├── TextFormatterService.java └── impl ├── AdditionCalculatorService.java ├── PrettyTextFormatterService.java ├── SimpleTextFormatterService.java └── SubtractionCalculatorService.java /.github/workflows/maven.yml: -------------------------------------------------------------------------------- 1 | name: Java CI with Maven 2 | 3 | on: 4 | push: 5 | branches: [ master ] 6 | pull_request: 7 | branches: [ master ] 8 | 9 | jobs: 10 | build: 11 | 12 | runs-on: ubuntu-latest 13 | 14 | strategy: 15 | matrix: 16 | java-version: [ '21' ] 17 | 18 | steps: 19 | - name: Checkout code 20 | uses: actions/checkout@v4 21 | 22 | - name: Set up JDK ${{ matrix.java-version }} 23 | uses: actions/setup-java@v4 24 | with: 25 | java-version: ${{ matrix.java-version }} 26 | distribution: 'temurin' 27 | 28 | - name: Build with Maven 29 | run: ./mvnw -B package --file pom.xml 30 | 31 | - name: Run tests 32 | run: ./mvnw test -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | .classpath 2 | .project 3 | .settings 4 | .idea 5 | *.iml 6 | /target 7 | -------------------------------------------------------------------------------- /.mvn/wrapper/maven-wrapper.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/zeldan/your-own-dependency-injection-framework/2782229f3d6f518aa9b9207647c90e8716674683/.mvn/wrapper/maven-wrapper.jar -------------------------------------------------------------------------------- /.mvn/wrapper/maven-wrapper.properties: -------------------------------------------------------------------------------- 1 | distributionUrl=https://repo1.maven.org/maven2/org/apache/maven/apache-maven/3.6.0/apache-maven-3.6.0-bin.zip 2 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright {yyyy} {name of copyright owner} 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # your-own-dependency-injection-framework 2 | 3 | ![Build Status](https://github.com/zeldan/your-own-dependency-injection-framework/actions/workflows/maven.yml/badge.svg) 4 | 5 | This is a small project that demonstrates how to build your own dependency injection framework. 6 | 7 | It supports **constructor** and **field** injection. 8 | 9 | - The framework itself can be found under the "com.di.framework" package. 10 | - Sample applications are available under the tests. 11 | 12 | ### How to use 13 | 14 | ##### 1. Define how you want to map interfaces to their implementations. 15 | 16 | ```java 17 | public class DependencyInjectionConfig extends AbstractModule { 18 | 19 | @Override 20 | public void configure() { 21 | createMapping(GreetingService.class, WelcomeServiceImpl.class); 22 | createMapping(Logger.class, QuietLoggerImpl.class); 23 | } 24 | } 25 | ``` 26 | 27 | ##### 2. Add **@OwnInject** annotation to the constructor or fields. 28 | 29 | ```java 30 | public class ConstructorInjectionClient { 31 | 32 | private final GreetingService service; 33 | private final Logger logger; 34 | 35 | @OwnInject 36 | public ConstructorInjectionClient(final GreetingService service, final Logger logger) { 37 | this.service = service; 38 | this.logger = logger; 39 | } 40 | } 41 | ``` 42 | 43 | OR 44 | 45 | ```java 46 | public class FieldInjectionClient { 47 | 48 | @OwnInject 49 | private GreetingService service; 50 | 51 | @OwnInject 52 | private Logger logger; 53 | 54 | } 55 | ``` 56 | 57 | ##### 3. Use **OwnDi** to get your injected class. 58 | 59 | ```java 60 | public class SampleAppToTryDependencyInjection { 61 | 62 | public static void main(final String[] args) throws Exception { 63 | final OwnDiFramework ownDi = OwnDi.getFramework(new DependencyInjectionConfig()); 64 | final ConstructorInjectionClient constructorInjectionClient = (ConstructorInjectionClient) ownDi.inject(ConstructorInjectionClient.class); 65 | } 66 | 67 | } 68 | ``` 69 | 70 | ### How It Works 71 | 72 | The two main classes are **AbstractModule** and **OwnDiFramework**. 73 | 74 | * **AbstractModule** contains interfaces with their implementations (subclasses). 75 | * **OwnDiFramework** performs the injection via Java reflection. It checks that the constructor or fields are annotated with the **@OwnInject** annotation. 76 | 77 | 78 | ### Running Tests 79 | 80 | To execute tests, use the Maven Wrapper included in the project. Run the following command from the root directory of the project: 81 | 82 | ```sh 83 | ./mvnw test 84 | ``` 85 | 86 | This command will compile the project with Java 21 and run all the tests using JUnit. 87 | 88 | If you encounter any issues or have any questions, please refer to the documentation or reach out for support. -------------------------------------------------------------------------------- /mvnw: -------------------------------------------------------------------------------- 1 | #!/bin/sh 2 | # ---------------------------------------------------------------------------- 3 | # Licensed to the Apache Software Foundation (ASF) under one 4 | # or more contributor license agreements. See the NOTICE file 5 | # distributed with this work for additional information 6 | # regarding copyright ownership. The ASF licenses this file 7 | # to you under the Apache License, Version 2.0 (the 8 | # "License"); you may not use this file except in compliance 9 | # with the License. You may obtain a copy of the License at 10 | # 11 | # http://www.apache.org/licenses/LICENSE-2.0 12 | # 13 | # Unless required by applicable law or agreed to in writing, 14 | # software distributed under the License is distributed on an 15 | # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 16 | # KIND, either express or implied. See the License for the 17 | # specific language governing permissions and limitations 18 | # under the License. 19 | # ---------------------------------------------------------------------------- 20 | 21 | # ---------------------------------------------------------------------------- 22 | # Maven2 Start Up Batch script 23 | # 24 | # Required ENV vars: 25 | # ------------------ 26 | # JAVA_HOME - location of a JDK home dir 27 | # 28 | # Optional ENV vars 29 | # ----------------- 30 | # M2_HOME - location of maven2's installed home dir 31 | # MAVEN_OPTS - parameters passed to the Java VM when running Maven 32 | # e.g. to debug Maven itself, use 33 | # set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000 34 | # MAVEN_SKIP_RC - flag to disable loading of mavenrc files 35 | # ---------------------------------------------------------------------------- 36 | 37 | if [ -z "$MAVEN_SKIP_RC" ] ; then 38 | 39 | if [ -f /etc/mavenrc ] ; then 40 | . /etc/mavenrc 41 | fi 42 | 43 | if [ -f "$HOME/.mavenrc" ] ; then 44 | . "$HOME/.mavenrc" 45 | fi 46 | 47 | fi 48 | 49 | # OS specific support. $var _must_ be set to either true or false. 50 | cygwin=false; 51 | darwin=false; 52 | mingw=false 53 | case "`uname`" in 54 | CYGWIN*) cygwin=true ;; 55 | MINGW*) mingw=true;; 56 | Darwin*) darwin=true 57 | # Use /usr/libexec/java_home if available, otherwise fall back to /Library/Java/Home 58 | # See https://developer.apple.com/library/mac/qa/qa1170/_index.html 59 | if [ -z "$JAVA_HOME" ]; then 60 | if [ -x "/usr/libexec/java_home" ]; then 61 | export JAVA_HOME="`/usr/libexec/java_home`" 62 | else 63 | export JAVA_HOME="/Library/Java/Home" 64 | fi 65 | fi 66 | ;; 67 | esac 68 | 69 | if [ -z "$JAVA_HOME" ] ; then 70 | if [ -r /etc/gentoo-release ] ; then 71 | JAVA_HOME=`java-config --jre-home` 72 | fi 73 | fi 74 | 75 | if [ -z "$M2_HOME" ] ; then 76 | ## resolve links - $0 may be a link to maven's home 77 | PRG="$0" 78 | 79 | # need this for relative symlinks 80 | while [ -h "$PRG" ] ; do 81 | ls=`ls -ld "$PRG"` 82 | link=`expr "$ls" : '.*-> \(.*\)$'` 83 | if expr "$link" : '/.*' > /dev/null; then 84 | PRG="$link" 85 | else 86 | PRG="`dirname "$PRG"`/$link" 87 | fi 88 | done 89 | 90 | saveddir=`pwd` 91 | 92 | M2_HOME=`dirname "$PRG"`/.. 93 | 94 | # make it fully qualified 95 | M2_HOME=`cd "$M2_HOME" && pwd` 96 | 97 | cd "$saveddir" 98 | # echo Using m2 at $M2_HOME 99 | fi 100 | 101 | # For Cygwin, ensure paths are in UNIX format before anything is touched 102 | if $cygwin ; then 103 | [ -n "$M2_HOME" ] && 104 | M2_HOME=`cygpath --unix "$M2_HOME"` 105 | [ -n "$JAVA_HOME" ] && 106 | JAVA_HOME=`cygpath --unix "$JAVA_HOME"` 107 | [ -n "$CLASSPATH" ] && 108 | CLASSPATH=`cygpath --path --unix "$CLASSPATH"` 109 | fi 110 | 111 | # For Migwn, ensure paths are in UNIX format before anything is touched 112 | if $mingw ; then 113 | [ -n "$M2_HOME" ] && 114 | M2_HOME="`(cd "$M2_HOME"; pwd)`" 115 | [ -n "$JAVA_HOME" ] && 116 | JAVA_HOME="`(cd "$JAVA_HOME"; pwd)`" 117 | # TODO classpath? 118 | fi 119 | 120 | if [ -z "$JAVA_HOME" ]; then 121 | javaExecutable="`which javac`" 122 | if [ -n "$javaExecutable" ] && ! [ "`expr \"$javaExecutable\" : '\([^ ]*\)'`" = "no" ]; then 123 | # readlink(1) is not available as standard on Solaris 10. 124 | readLink=`which readlink` 125 | if [ ! `expr "$readLink" : '\([^ ]*\)'` = "no" ]; then 126 | if $darwin ; then 127 | javaHome="`dirname \"$javaExecutable\"`" 128 | javaExecutable="`cd \"$javaHome\" && pwd -P`/javac" 129 | else 130 | javaExecutable="`readlink -f \"$javaExecutable\"`" 131 | fi 132 | javaHome="`dirname \"$javaExecutable\"`" 133 | javaHome=`expr "$javaHome" : '\(.*\)/bin'` 134 | JAVA_HOME="$javaHome" 135 | export JAVA_HOME 136 | fi 137 | fi 138 | fi 139 | 140 | if [ -z "$JAVACMD" ] ; then 141 | if [ -n "$JAVA_HOME" ] ; then 142 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then 143 | # IBM's JDK on AIX uses strange locations for the executables 144 | JAVACMD="$JAVA_HOME/jre/sh/java" 145 | else 146 | JAVACMD="$JAVA_HOME/bin/java" 147 | fi 148 | else 149 | JAVACMD="`which java`" 150 | fi 151 | fi 152 | 153 | if [ ! -x "$JAVACMD" ] ; then 154 | echo "Error: JAVA_HOME is not defined correctly." >&2 155 | echo " We cannot execute $JAVACMD" >&2 156 | exit 1 157 | fi 158 | 159 | if [ -z "$JAVA_HOME" ] ; then 160 | echo "Warning: JAVA_HOME environment variable is not set." 161 | fi 162 | 163 | CLASSWORLDS_LAUNCHER=org.codehaus.plexus.classworlds.launcher.Launcher 164 | 165 | # traverses directory structure from process work directory to filesystem root 166 | # first directory with .mvn subdirectory is considered project base directory 167 | find_maven_basedir() { 168 | 169 | if [ -z "$1" ] 170 | then 171 | echo "Path not specified to find_maven_basedir" 172 | return 1 173 | fi 174 | 175 | basedir="$1" 176 | wdir="$1" 177 | while [ "$wdir" != '/' ] ; do 178 | if [ -d "$wdir"/.mvn ] ; then 179 | basedir=$wdir 180 | break 181 | fi 182 | # workaround for JBEAP-8937 (on Solaris 10/Sparc) 183 | if [ -d "${wdir}" ]; then 184 | wdir=`cd "$wdir/.."; pwd` 185 | fi 186 | # end of workaround 187 | done 188 | echo "${basedir}" 189 | } 190 | 191 | # concatenates all lines of a file 192 | concat_lines() { 193 | if [ -f "$1" ]; then 194 | echo "$(tr -s '\n' ' ' < "$1")" 195 | fi 196 | } 197 | 198 | BASE_DIR=`find_maven_basedir "$(pwd)"` 199 | if [ -z "$BASE_DIR" ]; then 200 | exit 1; 201 | fi 202 | 203 | export MAVEN_PROJECTBASEDIR=${MAVEN_BASEDIR:-"$BASE_DIR"} 204 | echo $MAVEN_PROJECTBASEDIR 205 | MAVEN_OPTS="$(concat_lines "$MAVEN_PROJECTBASEDIR/.mvn/jvm.config") $MAVEN_OPTS" 206 | 207 | # For Cygwin, switch paths to Windows format before running java 208 | if $cygwin; then 209 | [ -n "$M2_HOME" ] && 210 | M2_HOME=`cygpath --path --windows "$M2_HOME"` 211 | [ -n "$JAVA_HOME" ] && 212 | JAVA_HOME=`cygpath --path --windows "$JAVA_HOME"` 213 | [ -n "$CLASSPATH" ] && 214 | CLASSPATH=`cygpath --path --windows "$CLASSPATH"` 215 | [ -n "$MAVEN_PROJECTBASEDIR" ] && 216 | MAVEN_PROJECTBASEDIR=`cygpath --path --windows "$MAVEN_PROJECTBASEDIR"` 217 | fi 218 | 219 | WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain 220 | 221 | exec "$JAVACMD" \ 222 | $MAVEN_OPTS \ 223 | -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \ 224 | "-Dmaven.home=${M2_HOME}" "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \ 225 | ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@" 226 | -------------------------------------------------------------------------------- /mvnw.cmd: -------------------------------------------------------------------------------- 1 | @REM ---------------------------------------------------------------------------- 2 | @REM Licensed to the Apache Software Foundation (ASF) under one 3 | @REM or more contributor license agreements. See the NOTICE file 4 | @REM distributed with this work for additional information 5 | @REM regarding copyright ownership. The ASF licenses this file 6 | @REM to you under the Apache License, Version 2.0 (the 7 | @REM "License"); you may not use this file except in compliance 8 | @REM with the License. You may obtain a copy of the License at 9 | @REM 10 | @REM http://www.apache.org/licenses/LICENSE-2.0 11 | @REM 12 | @REM Unless required by applicable law or agreed to in writing, 13 | @REM software distributed under the License is distributed on an 14 | @REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 | @REM KIND, either express or implied. See the License for the 16 | @REM specific language governing permissions and limitations 17 | @REM under the License. 18 | @REM ---------------------------------------------------------------------------- 19 | 20 | @REM ---------------------------------------------------------------------------- 21 | @REM Maven2 Start Up Batch script 22 | @REM 23 | @REM Required ENV vars: 24 | @REM JAVA_HOME - location of a JDK home dir 25 | @REM 26 | @REM Optional ENV vars 27 | @REM M2_HOME - location of maven2's installed home dir 28 | @REM MAVEN_BATCH_ECHO - set to 'on' to enable the echoing of the batch commands 29 | @REM MAVEN_BATCH_PAUSE - set to 'on' to wait for a key stroke before ending 30 | @REM MAVEN_OPTS - parameters passed to the Java VM when running Maven 31 | @REM e.g. to debug Maven itself, use 32 | @REM set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000 33 | @REM MAVEN_SKIP_RC - flag to disable loading of mavenrc files 34 | @REM ---------------------------------------------------------------------------- 35 | 36 | @REM Begin all REM lines with '@' in case MAVEN_BATCH_ECHO is 'on' 37 | @echo off 38 | @REM enable echoing my setting MAVEN_BATCH_ECHO to 'on' 39 | @if "%MAVEN_BATCH_ECHO%" == "on" echo %MAVEN_BATCH_ECHO% 40 | 41 | @REM set %HOME% to equivalent of $HOME 42 | if "%HOME%" == "" (set "HOME=%HOMEDRIVE%%HOMEPATH%") 43 | 44 | @REM Execute a user defined script before this one 45 | if not "%MAVEN_SKIP_RC%" == "" goto skipRcPre 46 | @REM check for pre script, once with legacy .bat ending and once with .cmd ending 47 | if exist "%HOME%\mavenrc_pre.bat" call "%HOME%\mavenrc_pre.bat" 48 | if exist "%HOME%\mavenrc_pre.cmd" call "%HOME%\mavenrc_pre.cmd" 49 | :skipRcPre 50 | 51 | @setlocal 52 | 53 | set ERROR_CODE=0 54 | 55 | @REM To isolate internal variables from possible post scripts, we use another setlocal 56 | @setlocal 57 | 58 | @REM ==== START VALIDATION ==== 59 | if not "%JAVA_HOME%" == "" goto OkJHome 60 | 61 | echo. 62 | echo Error: JAVA_HOME not found in your environment. >&2 63 | echo Please set the JAVA_HOME variable in your environment to match the >&2 64 | echo location of your Java installation. >&2 65 | echo. 66 | goto error 67 | 68 | :OkJHome 69 | if exist "%JAVA_HOME%\bin\java.exe" goto init 70 | 71 | echo. 72 | echo Error: JAVA_HOME is set to an invalid directory. >&2 73 | echo JAVA_HOME = "%JAVA_HOME%" >&2 74 | echo Please set the JAVA_HOME variable in your environment to match the >&2 75 | echo location of your Java installation. >&2 76 | echo. 77 | goto error 78 | 79 | @REM ==== END VALIDATION ==== 80 | 81 | :init 82 | 83 | @REM Find the project base dir, i.e. the directory that contains the folder ".mvn". 84 | @REM Fallback to current working directory if not found. 85 | 86 | set MAVEN_PROJECTBASEDIR=%MAVEN_BASEDIR% 87 | IF NOT "%MAVEN_PROJECTBASEDIR%"=="" goto endDetectBaseDir 88 | 89 | set EXEC_DIR=%CD% 90 | set WDIR=%EXEC_DIR% 91 | :findBaseDir 92 | IF EXIST "%WDIR%"\.mvn goto baseDirFound 93 | cd .. 94 | IF "%WDIR%"=="%CD%" goto baseDirNotFound 95 | set WDIR=%CD% 96 | goto findBaseDir 97 | 98 | :baseDirFound 99 | set MAVEN_PROJECTBASEDIR=%WDIR% 100 | cd "%EXEC_DIR%" 101 | goto endDetectBaseDir 102 | 103 | :baseDirNotFound 104 | set MAVEN_PROJECTBASEDIR=%EXEC_DIR% 105 | cd "%EXEC_DIR%" 106 | 107 | :endDetectBaseDir 108 | 109 | IF NOT EXIST "%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config" goto endReadAdditionalConfig 110 | 111 | @setlocal EnableExtensions EnableDelayedExpansion 112 | for /F "usebackq delims=" %%a in ("%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config") do set JVM_CONFIG_MAVEN_PROPS=!JVM_CONFIG_MAVEN_PROPS! %%a 113 | @endlocal & set JVM_CONFIG_MAVEN_PROPS=%JVM_CONFIG_MAVEN_PROPS% 114 | 115 | :endReadAdditionalConfig 116 | 117 | SET MAVEN_JAVA_EXE="%JAVA_HOME%\bin\java.exe" 118 | 119 | set WRAPPER_JAR="%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.jar" 120 | set WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain 121 | 122 | %MAVEN_JAVA_EXE% %JVM_CONFIG_MAVEN_PROPS% %MAVEN_OPTS% %MAVEN_DEBUG_OPTS% -classpath %WRAPPER_JAR% "-Dmaven.multiModuleProjectDirectory=%MAVEN_PROJECTBASEDIR%" %WRAPPER_LAUNCHER% %MAVEN_CONFIG% %* 123 | if ERRORLEVEL 1 goto error 124 | goto end 125 | 126 | :error 127 | set ERROR_CODE=1 128 | 129 | :end 130 | @endlocal & set ERROR_CODE=%ERROR_CODE% 131 | 132 | if not "%MAVEN_SKIP_RC%" == "" goto skipRcPost 133 | @REM check for post script, once with legacy .bat ending and once with .cmd ending 134 | if exist "%HOME%\mavenrc_post.bat" call "%HOME%\mavenrc_post.bat" 135 | if exist "%HOME%\mavenrc_post.cmd" call "%HOME%\mavenrc_post.cmd" 136 | :skipRcPost 137 | 138 | @REM pause the script if MAVEN_BATCH_PAUSE is set to 'on' 139 | if "%MAVEN_BATCH_PAUSE%" == "on" pause 140 | 141 | if "%MAVEN_TERMINATE_CMD%" == "on" exit %ERROR_CODE% 142 | 143 | exit /B %ERROR_CODE% 144 | -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 3 | 4.0.0 4 | 5 | com.di 6 | com.di 7 | 0.0.1-SNAPSHOT 8 | jar 9 | 10 | your-own-dependency-injection-framework 11 | https://github.com/zeldan/your-own-dependency-injection-framework 12 | 13 | 14 | UTF-8 15 | 21 16 | 21 17 | 18 | 19 | 20 | 21 | org.junit.jupiter 22 | junit-jupiter-api 23 | 5.10.2 24 | test 25 | 26 | 27 | org.junit.jupiter 28 | junit-jupiter-engine 29 | 5.10.2 30 | test 31 | 32 | 33 | 34 | 35 | 36 | 37 | org.apache.maven.plugins 38 | maven-compiler-plugin 39 | 3.8.1 40 | 41 | 21 42 | 21 43 | 44 | 45 | 46 | 47 | 48 | 49 | -------------------------------------------------------------------------------- /src/main/java/com/di/framework/OwnDi.java: -------------------------------------------------------------------------------- 1 | package com.di.framework; 2 | 3 | import com.di.framework.module.IModule; 4 | 5 | /** 6 | * It initializes the configuration (based on the configuration module). 7 | * The configuration means, that it binds the interfaces to their implementations. 8 | * 9 | * @author zeldan 10 | * 11 | */ 12 | public final class OwnDi { 13 | 14 | private OwnDi() { 15 | 16 | } 17 | 18 | public static OwnDiFramework getFramework(final IModule module) { 19 | module.configure(); 20 | return new OwnDiFramework(module); 21 | } 22 | } -------------------------------------------------------------------------------- /src/main/java/com/di/framework/OwnDiFramework.java: -------------------------------------------------------------------------------- 1 | package com.di.framework; 2 | 3 | import java.lang.reflect.Constructor; 4 | import java.lang.reflect.Field; 5 | import java.lang.reflect.InvocationTargetException; 6 | 7 | import com.di.framework.annotation.OwnInject; 8 | import com.di.framework.module.IModule; 9 | 10 | /** 11 | * Own Dependency Injection framework, it uses reflection (Constructor, Field) to find the dependency and inject it. 12 | * 13 | * @author zeldan 14 | * 15 | */ 16 | public class OwnDiFramework { 17 | 18 | private final IModule module; 19 | 20 | public OwnDiFramework(final IModule module) { 21 | this.module = module; 22 | } 23 | 24 | public Object inject(final Class classToInject) throws Exception { 25 | if (classToInject == null) { 26 | return null; 27 | } 28 | return injectFieldsIntoClass(classToInject); 29 | } 30 | 31 | private Object injectFieldsIntoClass(final Class classToInject) 32 | throws InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException { 33 | for (final Constructor constructor : classToInject.getConstructors()) { 34 | if (constructor.isAnnotationPresent(OwnInject.class)) { 35 | return injectFieldsViaConstructor(classToInject, constructor); 36 | } else { 37 | return injectFields(classToInject); 38 | } 39 | } 40 | return null; 41 | } 42 | 43 | private Object injectFields(Class classToInject) throws InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException { 44 | Object o = classToInject.newInstance(); 45 | for (Field field : classToInject.getDeclaredFields()) { 46 | if(field.isAnnotationPresent(OwnInject.class)) { 47 | final Class dependency = module.getMapping(field.getType()); 48 | field.setAccessible(true); 49 | field.set(o, dependency.getConstructor().newInstance()); 50 | } 51 | } 52 | return o; 53 | } 54 | 55 | private Object injectFieldsViaConstructor(Class classToInject, Constructor constructor) throws InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException { 56 | final Class[] parameterTypes = constructor.getParameterTypes(); 57 | final Object[] objArr = new Object[parameterTypes.length]; 58 | int i = 0; 59 | for (final Class c : parameterTypes) { 60 | final Class dependency = module.getMapping(c); 61 | if (c.isAssignableFrom(dependency)) { 62 | objArr[i++] = dependency.getConstructor().newInstance(); 63 | } 64 | } 65 | return classToInject.getConstructor(parameterTypes).newInstance(objArr); 66 | } 67 | } -------------------------------------------------------------------------------- /src/main/java/com/di/framework/annotation/OwnInject.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.annotation; 2 | 3 | import static java.lang.annotation.ElementType.CONSTRUCTOR; 4 | import static java.lang.annotation.ElementType.FIELD; 5 | import static java.lang.annotation.RetentionPolicy.RUNTIME; 6 | 7 | import java.lang.annotation.Documented; 8 | import java.lang.annotation.Retention; 9 | import java.lang.annotation.Target; 10 | 11 | /** 12 | * Custom annotation on constructor to indicate to the framework to inject the proper implementation. 13 | * 14 | * @author zeldan 15 | * 16 | */ 17 | @Target({CONSTRUCTOR, FIELD}) 18 | @Retention(RUNTIME) 19 | @Documented 20 | public @interface OwnInject { 21 | } -------------------------------------------------------------------------------- /src/main/java/com/di/framework/module/IModule.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.module; 2 | 3 | /** 4 | * Module interface to configure dependency injection mapping. 5 | * 6 | * @author zeldan 7 | * 8 | */ 9 | public interface IModule { 10 | 11 | void configure(); 12 | 13 | Class getMapping(Class type); 14 | } 15 | -------------------------------------------------------------------------------- /src/main/java/com/di/framework/module/impl/AbstractModule.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.module.impl; 2 | 3 | import java.util.HashMap; 4 | import java.util.Map; 5 | 6 | import com.di.framework.module.IModule; 7 | 8 | /** 9 | * Abstract module to configure and retrieve proper dependency injection mapping. 10 | * 11 | * @author zeldan 12 | * 13 | */ 14 | public abstract class AbstractModule implements IModule { 15 | 16 | private final Map, Class> classMap = new HashMap<>(); 17 | 18 | protected void createMapping(final Class baseClass, final Class subClass) { 19 | classMap.put(baseClass, subClass.asSubclass(baseClass)); 20 | } 21 | 22 | @Override 23 | public Class getMapping(final Class type) { 24 | final Class implementation = classMap.get(type); 25 | if (implementation == null) { 26 | throw new IllegalArgumentException("Couldn't find the mapping (subclass / implementation) for : " + type); 27 | } 28 | return implementation.asSubclass(type); 29 | } 30 | } 31 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/OwnDiFrameworkTest.java: -------------------------------------------------------------------------------- 1 | package com.di.framework; 2 | 3 | 4 | import static org.junit.jupiter.api.Assertions.assertEquals; 5 | 6 | import org.junit.jupiter.api.Test; 7 | 8 | import com.di.framework.example.ConstructorInjectionExample; 9 | 10 | import com.di.framework.example.FieldInjectionExample; 11 | import com.di.framework.example.service.CalculatorService; 12 | import com.di.framework.example.service.TextFormatterService; 13 | import com.di.framework.example.service.impl.AdditionCalculatorService; 14 | import com.di.framework.example.service.impl.PrettyTextFormatterService; 15 | import com.di.framework.example.service.impl.SimpleTextFormatterService; 16 | import com.di.framework.example.service.impl.SubtractionCalculatorService; 17 | import com.di.framework.module.impl.AbstractModule; 18 | 19 | public class OwnDiFrameworkTest { 20 | 21 | @Test 22 | public void shouldInjectPrettyTextFormatterAndAdditionCalculatorViaFieldInjection() throws Exception { 23 | OwnDiFramework ownDi = OwnDi.getFramework(new DependencyInjectionConfigExample1()); 24 | FieldInjectionExample example = (FieldInjectionExample) ownDi.inject(FieldInjectionExample.class); 25 | 26 | String processNumbers = example.processNumbers(3, 2); 27 | 28 | assertEquals("Pretty text: <5>", processNumbers); 29 | } 30 | 31 | @Test 32 | public void shouldInjectSimpleTextFormatterAndAdditionCalculatorViaFieldInjection() throws Exception { 33 | OwnDiFramework ownDi = OwnDi.getFramework(new DependencyInjectionConfigExample2()); 34 | FieldInjectionExample example = (FieldInjectionExample) ownDi.inject(FieldInjectionExample.class); 35 | 36 | String processNumbers = example.processNumbers(3, 2); 37 | 38 | assertEquals("Simple text: 5", processNumbers); 39 | } 40 | 41 | @Test 42 | public void shouldInjectSimpleTextFormatterAndSubtractionCalculatorViaConstructorInjection() throws Exception { 43 | OwnDiFramework ownDi = OwnDi.getFramework(new DependencyInjectionConfigExample3()); 44 | ConstructorInjectionExample example = (ConstructorInjectionExample) ownDi.inject(ConstructorInjectionExample.class); 45 | 46 | String processNumbers = example.processNumbers(3, 2); 47 | 48 | assertEquals("Simple text: 1", processNumbers); 49 | } 50 | 51 | private class DependencyInjectionConfigExample1 extends AbstractModule { 52 | 53 | @Override 54 | public void configure() { 55 | createMapping(CalculatorService.class, AdditionCalculatorService.class); 56 | createMapping(TextFormatterService.class, PrettyTextFormatterService.class); 57 | } 58 | } 59 | 60 | private class DependencyInjectionConfigExample2 extends AbstractModule { 61 | 62 | @Override 63 | public void configure() { 64 | createMapping(CalculatorService.class, AdditionCalculatorService.class); 65 | createMapping(TextFormatterService.class, SimpleTextFormatterService.class); 66 | } 67 | } 68 | 69 | private class DependencyInjectionConfigExample3 extends AbstractModule { 70 | 71 | @Override 72 | public void configure() { 73 | createMapping(CalculatorService.class, SubtractionCalculatorService.class); 74 | createMapping(TextFormatterService.class, SimpleTextFormatterService.class); 75 | } 76 | } 77 | 78 | } 79 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/ConstructorInjectionExample.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example; 2 | 3 | import com.di.framework.annotation.OwnInject; 4 | import com.di.framework.example.service.CalculatorService; 5 | import com.di.framework.example.service.TextFormatterService; 6 | 7 | public class ConstructorInjectionExample { 8 | 9 | private final CalculatorService calculatorService; 10 | private final TextFormatterService textFormatterService; 11 | 12 | @OwnInject 13 | public ConstructorInjectionExample(CalculatorService calculatorService, TextFormatterService textFormatterService) { 14 | this.calculatorService = calculatorService; 15 | this.textFormatterService = textFormatterService; 16 | } 17 | 18 | public String processNumbers(int firstNumber, int secondNumber) { 19 | int number = calculatorService.calculate(firstNumber, secondNumber); 20 | return textFormatterService.format(String.valueOf(number)); 21 | } 22 | } -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/FieldInjectionExample.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example; 2 | 3 | import com.di.framework.annotation.OwnInject; 4 | import com.di.framework.example.service.CalculatorService; 5 | import com.di.framework.example.service.TextFormatterService; 6 | 7 | public class FieldInjectionExample { 8 | 9 | @OwnInject 10 | private CalculatorService calculatorService; 11 | 12 | @OwnInject 13 | private TextFormatterService textFormatterService; 14 | 15 | public String processNumbers(int firstNumber, int secondNumber) { 16 | int number = calculatorService.calculate(firstNumber, secondNumber); 17 | return textFormatterService.format(String.valueOf(number)); 18 | } 19 | } -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/CalculatorService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service; 2 | 3 | public interface CalculatorService { 4 | 5 | int calculate(int firstNumber, int secondNumber); 6 | } 7 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/TextFormatterService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service; 2 | 3 | public interface TextFormatterService { 4 | 5 | String format(String text); 6 | } 7 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/impl/AdditionCalculatorService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service.impl; 2 | 3 | import com.di.framework.example.service.CalculatorService; 4 | 5 | public class AdditionCalculatorService implements CalculatorService { 6 | 7 | @Override 8 | public int calculate(int firstNumber, int secondNumber) { 9 | return firstNumber + secondNumber; 10 | } 11 | 12 | } 13 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/impl/PrettyTextFormatterService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service.impl; 2 | 3 | import com.di.framework.example.service.TextFormatterService; 4 | 5 | public class PrettyTextFormatterService implements TextFormatterService { 6 | 7 | @Override 8 | public String format(String text) { 9 | return "Pretty text: <" + text + ">"; 10 | } 11 | 12 | } 13 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/impl/SimpleTextFormatterService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service.impl; 2 | 3 | import com.di.framework.example.service.TextFormatterService; 4 | 5 | public class SimpleTextFormatterService implements TextFormatterService { 6 | 7 | @Override 8 | public String format(String text) { 9 | return "Simple text: " + text; 10 | } 11 | 12 | } 13 | -------------------------------------------------------------------------------- /src/test/java/com/di/framework/example/service/impl/SubtractionCalculatorService.java: -------------------------------------------------------------------------------- 1 | package com.di.framework.example.service.impl; 2 | 3 | import com.di.framework.example.service.CalculatorService; 4 | 5 | public class SubtractionCalculatorService implements CalculatorService { 6 | 7 | @Override 8 | public int calculate(int firstNumber, int secondNumber) { 9 | return firstNumber - secondNumber; 10 | } 11 | 12 | } 13 | --------------------------------------------------------------------------------