是否可以将两个JSON文档与Jackson JSON库合并？我基本上使用Jackson mapper和简单的Java Maps。
我试图在Google和Jackson的文档中搜索但找不到任何内容。
答案 0 :(得分：53)
受到StaxMans答案的启发，我实现了这种合并方法。
public static JsonNode merge(JsonNode mainNode, JsonNode updateNode) {
Iterator<String> fieldNames = updateNode.fieldNames();
while (fieldNames.hasNext()) {
String fieldName = fieldNames.next();
JsonNode jsonNode = mainNode.get(fieldName);
// if field exists and is an embedded object
if (jsonNode != null && jsonNode.isObject()) {
merge(jsonNode, updateNode.get(fieldName));
}
else {
if (mainNode instanceof ObjectNode) {
// Overwrite field
JsonNode value = updateNode.get(fieldName);
((ObjectNode) mainNode).put(fieldName, value);
}
}
}
return mainNode;
}
希望这有助于某人。
答案 1 :(得分：43)
一种方法是使用ObjectReader，如下所示：
MyBean defaults = objectMapper.readValue(defaultJson, MyBean.class);
ObjectReader updater = objectMapper.readerForUpdating(defaults);
MyBean merged = updater.readValue(overridesJson);
将合并来自两个来源的数据。这只会产生浅拷贝，即不对包含的对象进行递归合并。
否则，您可能只需将JSON读取为树（JsonNode），循环内容并手动合并。这通常是有道理的，因为合并的规则并不是微不足道的，每个人都有自己的合并应该如何运作的想法。
编辑 :( 2017年4月3日）
根据@Fernando Correia的评论，在即将到来的Jackson 2.9（将于2017年4月或5月发布）中添加了一个新的feature，最终允许深度合并。
答案 2 :(得分：10)
受到Arn的回答的启发。编辑它以添加节点可能包含节点数组的情况。
public static JsonNode merge(JsonNode mainNode, JsonNode updateNode) {
Iterator<String> fieldNames = updateNode.fieldNames();
while (fieldNames.hasNext()) {
String updatedFieldName = fieldNames.next();
JsonNode valueToBeUpdated = mainNode.get(updatedFieldName);
JsonNode updatedValue = updateNode.get(updatedFieldName);
// If the node is an @ArrayNode
if (valueToBeUpdated != null && valueToBeUpdated.isArray() &&
updatedValue.isArray()) {
// running a loop for all elements of the updated ArrayNode
for (int i = 0; i < updatedValue.size(); i++) {
JsonNode updatedChildNode = updatedValue.get(i);
// Create a new Node in the node that should be updated, if there was no corresponding node in it
// Use-case - where the updateNode will have a new element in its Array
if (valueToBeUpdated.size() <= i) {
((ArrayNode) valueToBeUpdated).add(updatedChildNode);
}
// getting reference for the node to be updated
JsonNode childNodeToBeUpdated = valueToBeUpdated.get(i);
merge(childNodeToBeUpdated, updatedChildNode);
}
// if the Node is an @ObjectNode
} else if (valueToBeUpdated != null && valueToBeUpdated.isObject()) {
merge(valueToBeUpdated, updatedValue);
} else {
if (mainNode instanceof ObjectNode) {
((ObjectNode) mainNode).replace(updatedFieldName, updatedValue);
}
}
}
return mainNode;
}
答案 3 :(得分：4)
以下是Scala中的实现。源节点和目标节点大多是可交换的，除非源和目标都存在分支。
def mergeYamlObjects(source: ObjectNode, target: ObjectNode, overwrite: Boolean = true): ObjectNode = {
if (target == null)
source
else if (source == null)
target
else {
val result = source.deepCopy
val fieldlist = source.fieldNames.asScala.toList ++ target.fieldNames.asScala.toList
for (item <- fieldlist) {
if (!(source has item)) {
result put(item, target get item)
} else {
if ((source get item).isValueNode) {
if (target has item)
if (overwrite)
result.put(item, target get item)
} else {
result.put(item, mergeYamlObjects(source.get(item).asInstanceOf[ObjectNode],
target.get(item).asInstanceOf[ObjectNode], overwrite = overwrite))
}
}
}
result
}
}
答案 4 :(得分：3)
如果有人只想将两个或多个JsonNode对象添加到一个JsonNode中，这可能是一种方法：
ArrayNode arrayNode = objectMapper.createArrayNode();
arrayNode.add(firstJsonNode);
arrayNode.add(secondJsonNode);
arrayNode.add(thirdJsonNode);
JsonNode root = JsonNodeFactory.instance.objectNode();
((ObjectNode) root).put("", arrayNode);
System.out.println("merged array node #: " + root);
答案 5 :(得分：2)
这里，将两个JSON树合并为一个完全实现。希望它会有所帮助:)）
; ModuleID = 'LLVMIRTest.m'
source_filename = "LLVMIRTest.m"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.12.0"
%struct._objc_cache = type opaque
%struct._class_t = type { %struct._class_t*, %struct._class_t*, %struct._objc_cache*, i8* (i8*, i8*)**, %struct._class_ro_t* }
%struct._class_ro_t = type { i32, i32, i32, i8*, i8*, %struct.__method_list_t*, %struct._objc_protocol_list*, %struct._ivar_list_t*, i8*, %struct._prop_list_t* }
%struct.__method_list_t = type { i32, i32, [0 x %struct._objc_method] }
%struct._objc_method = type { i8*, i8*, i8* }
%struct._objc_protocol_list = type { i64, [0 x %struct._protocol_t*] }
%struct._protocol_t = type { i8*, i8*, %struct._objc_protocol_list*, %struct.__method_list_t*, %struct.__method_list_t*, %struct.__method_list_t*, %struct.__method_list_t*, %struct._prop_list_t*, i32, i32, i8**, i8*, %struct._prop_list_t* }
%struct._ivar_list_t = type { i32, i32, [0 x %struct._ivar_t] }
%struct._ivar_t = type { i64*, i8*, i8*, i32, i32 }
%struct._prop_list_t = type { i32, i32, [0 x %struct._prop_t] }
%struct._prop_t = type { i8*, i8* }
@_objc_empty_cache = external global %struct._objc_cache
@"OBJC_METACLASS_$_NSObject" = external global %struct._class_t
@OBJC_CLASS_NAME_ = private global [11 x i8] c"LLVMIRTest\00", section "__TEXT,__objc_classname,cstring_literals", align 1
@"\01l_OBJC_METACLASS_RO_$_LLVMIRTest" = private global %struct._class_ro_t { i32 1, i32 40, i32 40, i8* null, i8* getelementptr inbounds ([11 x i8], [11 x i8]* @OBJC_CLASS_NAME_, i32 0, i32 0), %struct.__method_list_t* null, %struct._objc_protocol_list* null, %struct._ivar_list_t* null, i8* null, %struct._prop_list_t* null }, section "__DATA, __objc_const", align 8
@"OBJC_METACLASS_$_LLVMIRTest" = global %struct._class_t { %struct._class_t* @"OBJC_METACLASS_$_NSObject", %struct._class_t* @"OBJC_METACLASS_$_NSObject", %struct._objc_cache* @_objc_empty_cache, i8* (i8*, i8*)** null, %struct._class_ro_t* @"\01l_OBJC_METACLASS_RO_$_LLVMIRTest" }, section "__DATA, __objc_data", align 8
@"OBJC_CLASS_$_NSObject" = external global %struct._class_t
@"OBJC_IVAR_$_LLVMIRTest.ivarTest" = hidden global i64 8, section "__DATA, __objc_ivar", align 8
@OBJC_METH_VAR_NAME_ = private global [9 x i8] c"ivarTest\00", section "__TEXT,__objc_methname,cstring_literals", align 1
@OBJC_METH_VAR_TYPE_ = private global [12 x i8] c"@\22NSString\22\00", section "__TEXT,__objc_methtype,cstring_literals", align 1
@"\01l_OBJC_$_INSTANCE_VARIABLES_LLVMIRTest" = private global { i32, i32, [1 x %struct._ivar_t] } { i32 32, i32 1, [1 x %struct._ivar_t] [%struct._ivar_t { i64* @"OBJC_IVAR_$_LLVMIRTest.ivarTest", i8* getelementptr inbounds ([9 x i8], [9 x i8]* @OBJC_METH_VAR_NAME_, i32 0, i32 0), i8* getelementptr inbounds ([12 x i8], [12 x i8]* @OBJC_METH_VAR_TYPE_, i32 0, i32 0), i32 3, i32 8 }] }, section "__DATA, __objc_const", align 8
@"\01l_OBJC_CLASS_RO_$_LLVMIRTest" = private global %struct._class_ro_t { i32 0, i32 8, i32 16, i8* null, i8* getelementptr inbounds ([11 x i8], [11 x i8]* @OBJC_CLASS_NAME_, i32 0, i32 0), %struct.__method_list_t* null, %struct._objc_protocol_list* null, %struct._ivar_list_t* bitcast ({ i32, i32, [1 x %struct._ivar_t] }* @"\01l_OBJC_$_INSTANCE_VARIABLES_LLVMIRTest" to %struct._ivar_list_t*), i8* null, %struct._prop_list_t* null }, section "__DATA, __objc_const", align 8
@"OBJC_CLASS_$_LLVMIRTest" = global %struct._class_t { %struct._class_t* @"OBJC_METACLASS_$_LLVMIRTest", %struct._class_t* @"OBJC_CLASS_$_NSObject", %struct._objc_cache* @_objc_empty_cache, i8* (i8*, i8*)** null, %struct._class_ro_t* @"\01l_OBJC_CLASS_RO_$_LLVMIRTest" }, section "__DATA, __objc_data", align 8
@"OBJC_LABEL_CLASS_$" = private global [1 x i8*] [i8* bitcast (%struct._class_t* @"OBJC_CLASS_$_LLVMIRTest" to i8*)], section "__DATA, __objc_classlist, regular, no_dead_strip", align 8
@llvm.compiler.used = appending global [5 x i8*] [i8* getelementptr inbounds ([11 x i8], [11 x i8]* @OBJC_CLASS_NAME_, i32 0, i32 0), i8* getelementptr inbounds ([9 x i8], [9 x i8]* @OBJC_METH_VAR_NAME_, i32 0, i32 0), i8* getelementptr inbounds ([12 x i8], [12 x i8]* @OBJC_METH_VAR_TYPE_, i32 0, i32 0), i8* bitcast ({ i32, i32, [1 x %struct._ivar_t] }* @"\01l_OBJC_$_INSTANCE_VARIABLES_LLVMIRTest" to i8*), i8* bitcast ([1 x i8*]* @"OBJC_LABEL_CLASS_$" to i8*)], section "llvm.metadata"
!llvm.module.flags = !{!0, !1, !2, !3, !4, !5}
!llvm.ident = !{!6}
!0 = !{i32 1, !"Objective-C Version", i32 2}
!1 = !{i32 1, !"Objective-C Image Info Version", i32 0}
!2 = !{i32 1, !"Objective-C Image Info Section", !"__DATA, __objc_imageinfo, regular, no_dead_strip"}
!3 = !{i32 4, !"Objective-C Garbage Collection", i32 0}
!4 = !{i32 1, !"Objective-C Class Properties", i32 64}
!5 = !{i32 1, !"PIC Level", i32 2}
!6 = !{!"Apple LLVM version 8.0.0 (clang-800.0.38)"}