While this class is neither feature-rich nor the most performant one, it's sufficient enough 680 | * for its use-case. 681 | */ 682 | public static class JsonObjectBuilder { 683 | 684 | private StringBuilder builder = new StringBuilder(); 685 | 686 | private boolean hasAtLeastOneField = false; 687 | 688 | public JsonObjectBuilder() { 689 | builder.append("{"); 690 | } 691 | 692 | /** 693 | * Appends a null field to the JSON. 694 | * 695 | * @param key The key of the field. 696 | * @return A reference to this object. 697 | */ 698 | public JsonObjectBuilder appendNull(String key) { 699 | appendFieldUnescaped(key, "null"); 700 | return this; 701 | } 702 | 703 | /** 704 | * Appends a string field to the JSON. 705 | * 706 | * @param key The key of the field. 707 | * @param value The value of the field. 708 | * @return A reference to this object. 709 | */ 710 | public JsonObjectBuilder appendField(String key, String value) { 711 | if (value == null) { 712 | throw new IllegalArgumentException("JSON value must not be null"); 713 | } 714 | appendFieldUnescaped(key, "\"" + escape(value) + "\""); 715 | return this; 716 | } 717 | 718 | /** 719 | * Appends an integer field to the JSON. 720 | * 721 | * @param key The key of the field. 722 | * @param value The value of the field. 723 | * @return A reference to this object. 724 | */ 725 | public JsonObjectBuilder appendField(String key, int value) { 726 | appendFieldUnescaped(key, String.valueOf(value)); 727 | return this; 728 | } 729 | 730 | /** 731 | * Appends an object to the JSON. 732 | * 733 | * @param key The key of the field. 734 | * @param object The object. 735 | * @return A reference to this object. 736 | */ 737 | public JsonObjectBuilder appendField(String key, JsonObject object) { 738 | if (object == null) { 739 | throw new IllegalArgumentException("JSON object must not be null"); 740 | } 741 | appendFieldUnescaped(key, object.toString()); 742 | return this; 743 | } 744 | 745 | /** 746 | * Appends a string array to the JSON. 747 | * 748 | * @param key The key of the field. 749 | * @param values The string array. 750 | * @return A reference to this object. 751 | */ 752 | public JsonObjectBuilder appendField(String key, String[] values) { 753 | if (values == null) { 754 | throw new IllegalArgumentException("JSON values must not be null"); 755 | } 756 | String escapedValues = 757 | Arrays.stream(values) 758 | .map(value -> "\"" + escape(value) + "\"") 759 | .collect(Collectors.joining(",")); 760 | appendFieldUnescaped(key, "[" + escapedValues + "]"); 761 | return this; 762 | } 763 | 764 | /** 765 | * Appends an integer array to the JSON. 766 | * 767 | * @param key The key of the field. 768 | * @param values The integer array. 769 | * @return A reference to this object. 770 | */ 771 | public JsonObjectBuilder appendField(String key, int[] values) { 772 | if (values == null) { 773 | throw new IllegalArgumentException("JSON values must not be null"); 774 | } 775 | String escapedValues = 776 | Arrays.stream(values).mapToObj(String::valueOf).collect(Collectors.joining(",")); 777 | appendFieldUnescaped(key, "[" + escapedValues + "]"); 778 | return this; 779 | } 780 | 781 | /** 782 | * Appends an object array to the JSON. 783 | * 784 | * @param key The key of the field. 785 | * @param values The integer array. 786 | * @return A reference to this object. 787 | */ 788 | public JsonObjectBuilder appendField(String key, JsonObject[] values) { 789 | if (values == null) { 790 | throw new IllegalArgumentException("JSON values must not be null"); 791 | } 792 | String escapedValues = 793 | Arrays.stream(values).map(JsonObject::toString).collect(Collectors.joining(",")); 794 | appendFieldUnescaped(key, "[" + escapedValues + "]"); 795 | return this; 796 | } 797 | 798 | /** 799 | * Appends a field to the object. 800 | * 801 | * @param key The key of the field. 802 | * @param escapedValue The escaped value of the field. 803 | */ 804 | private void appendFieldUnescaped(String key, String escapedValue) { 805 | if (builder == null) { 806 | throw new IllegalStateException("JSON has already been built"); 807 | } 808 | if (key == null) { 809 | throw new IllegalArgumentException("JSON key must not be null"); 810 | } 811 | if (hasAtLeastOneField) { 812 | builder.append(","); 813 | } 814 | builder.append("\"").append(escape(key)).append("\":").append(escapedValue); 815 | hasAtLeastOneField = true; 816 | } 817 | 818 | /** 819 | * Builds the JSON string and invalidates this builder. 820 | * 821 | * @return The built JSON string. 822 | */ 823 | public JsonObject build() { 824 | if (builder == null) { 825 | throw new IllegalStateException("JSON has already been built"); 826 | } 827 | JsonObject object = new JsonObject(builder.append("}").toString()); 828 | builder = null; 829 | return object; 830 | } 831 | 832 | /** 833 | * Escapes the given string like stated in https://www.ietf.org/rfc/rfc4627.txt. 834 | * 835 | *
This method escapes only the necessary characters '"', '\'. and '\u0000' - '\u001F'. 836 | * Compact escapes are not used (e.g., '\n' is escaped as "\u000a" and not as "\n"). 837 | * 838 | * @param value The value to escape. 839 | * @return The escaped value. 840 | */ 841 | private static String escape(String value) { 842 | final StringBuilder builder = new StringBuilder(); 843 | for (int i = 0; i < value.length(); i++) { 844 | char c = value.charAt(i); 845 | if (c == '"') { 846 | builder.append("\\\""); 847 | } else if (c == '\\') { 848 | builder.append("\\\\"); 849 | } else if (c <= '\u000F') { 850 | builder.append("\\u000").append(Integer.toHexString(c)); 851 | } else if (c <= '\u001F') { 852 | builder.append("\\u00").append(Integer.toHexString(c)); 853 | } else { 854 | builder.append(c); 855 | } 856 | } 857 | return builder.toString(); 858 | } 859 | 860 | /** 861 | * A super simple representation of a JSON object. 862 | * 863 | *
This class only exists to make methods of the {@link JsonObjectBuilder} type-safe and not 864 | * allow a raw string inputs for methods like {@link JsonObjectBuilder#appendField(String, 865 | * JsonObject)}. 866 | */ 867 | public static class JsonObject { 868 | 869 | private final String value; 870 | 871 | private JsonObject(String value) { 872 | this.value = value; 873 | } 874 | 875 | @Override 876 | public String toString() { 877 | return value; 878 | } 879 | } 880 | } 881 | } --------------------------------------------------------------------------------