Fastjson2基础使用以及底层序列化/反序列化实现探究
1 Fastjson2简介
Fastjson2是Fastjson的升级版，特征：
- 协议支持：支持
JSON/JSONB两种协议 - 部分解析：可以使用
JSONPath进行部分解析获取需要的值 - 语言支持：
Java/Kotlin - 场景支持：
Android8+/服务端 - 其他特性支持：
Graal Native-Image、JSON Schema
2 基础使用
2.1 测试环境
环境：
JDK版本：1.8.0_341Fastjson2版本：2.0.19
测试类：
@Builder
@Data
@ToString
public class Entity {
private String field1;
private Integer field2;
}
2.2 JSON序列化
System.out.println(JSON.toJSONString(entity));
2.3 JSON反序列化
System.out.println(JSON.parseObject(str,Entity.class));
2.4 JSONB序列化
byte[] bytes = JSONB.toBytes(entity);
2.5 JSONB反序列化
System.out.println(JSONB.parseObject(bytes,Entity.class));
2.6 JSON Schema
JSON Schema可用于反序列化时对JSON字段进行验证使用，配置Schema可以通过@JSONField/@JSONType，这里以@JSONField为例：
public class Entity {
private String field1;
@JSONField(schema = "{'minimum':0,'maximum':100}")
private Integer field2;
}
测试代码：
Entity entity1 = Entity.builder().field2(-1).build();
Entity entity2 = Entity.builder().field2(50).build();
Entity entity3 = Entity.builder().field2(101).build();
String str1 = JSON.toJSONString(entity1);
String str2 = JSON.toJSONString(entity2);
String str3 = JSON.toJSONString(entity3);
try {
JSON.parseObject(str1, Entity.class);
} catch (Exception e) {
e.printStackTrace();
}
JSON.parseObject(str2, Entity.class);
try {
JSON.parseObject(str3, Entity.class);
} catch (Exception e) {
e.printStackTrace();
}
输出：
2.7 JSONPath
JSONPath可用于部分解析JSON字符串，示例：
Entity entity = Entity.builder().field1("a").field2(2).build();
// $符号表示根对象
// $.field1表示根对象的field1属性
System.out.println(JSONPath.eval(entity,"$.field1"));
System.out.println(JSONPath.eval(entity,"$.field2"));
List<Entity> list = new ArrayList<>();
list.add(Entity.builder().field1("entity1").field2(1).build());
list.add(Entity.builder().field1("entity2").field2(2).build());
// 如果传的是List，支持通过下标解析
// 此处是返回[0,0]下标范围内的值
List<Entity> names = (List<Entity>)JSONPath.eval(list,"[0,0]");
System.out.println(names.get(0));
详细的解析语法以及更多例子请参考官方文档。
2.8 AutoType
AutoType是在序列化的时候带上类型的一种机制，这样在反序列化时就不需要传入类型，实现类型自动识别，例子：
Entity entity = Entity.builder().field1("a").field2(2).build();
String str = JSON.toJSONString(entity, JSONWriter.Feature.WriteClassName);
System.out.println(str);
System.out.println(JSON.parseObject(str, Object.class, JSONReader.Feature.SupportAutoType));
输出：
由于在Fastjson1中出现过AutoType漏洞，因此官方提供了一个JVM参数完全禁止（safeMode功能）：
-Dfastjson2.parser.safeMode=true
3 底层实现探究
3.1 序列化
3.1.1 概览
序列化的实现可以参考官方的一张类图：
大概流程如下：
- 获取
ObjectWriter - 如果从
ObjectWriterProvider缓存有ObjectWriter，直接提取 - 如果
ObjectWriterProvider缓存没有ObjectWriter，构造对应的ObjectWriter，并缓存 - 获取到
ObjectWriter后，将JavaBean对象写入JSONWriter JSONWriter对基础类型进行写入- 返回结果
3.1.2 入口
这里的序列化探究以JSON.toJSONString(Object object)作为入口：
static String toJSONString(Object object) {
// 初始化ObjectWriterProvider
JSONWriter.Context writeContext = new JSONWriter.Context(JSONFactory.defaultObjectWriterProvider);
// 格式化控制
boolean pretty = (writeContext.features & com.alibaba.fastjson2.JSONWriter.Feature.PrettyFormat.mask) != 0L;
Object jsonWriter;
// 默认有三个JSONWriter，JDK8一个，针对JDK9之后的byte[]实现的字符串优化也有一个，还有一个基于char[]实现的UTF16
if (JDKUtils.JVM_VERSION == 8) {
jsonWriter = new JSONWriterUTF16JDK8(writeContext);
} else if ((writeContext.features & com.alibaba.fastjson2.JSONWriter.Feature.OptimizedForAscii.mask) != 0L) {
jsonWriter = new JSONWriterUTF8JDK9(writeContext);
} else {
jsonWriter = new JSONWriterUTF16(writeContext);
}
try {
// 格式化控制
JSONWriter writer = pretty ? new JSONWriterPretty((JSONWriter)jsonWriter) : jsonWriter;
String var12;
try {
if (object == null) {
// null的话直接写入"null"字符串
((JSONWriter)writer).writeNull();
} else {
// 设置根对象
((JSONWriter)writer).setRootObject(object);
Class<?> valueClass = object.getClass();
if (valueClass == JSONObject.class) {
// 如果目标类是JSNOObject，直接调用writer的write方法
((JSONWriter)writer).write((JSONObject)object);
} else {
// 如果不是
JSONWriter.Context context = ((JSONWriter)writer).context;
boolean fieldBased = (context.features & com.alibaba.fastjson2.JSONWriter.Feature.FieldBased.mask) != 0L;
// 通过Provider获取ObjectWriter
ObjectWriter<?> objectWriter = context.provider.getObjectWriter(valueClass, valueClass, fieldBased);
// ObjectWriter将数据写入JSONWriter
objectWriter.write((JSONWriter)writer, object, (Object)null, (Type)null, 0L);
}
}
// 结果
var12 = writer.toString();
// 下面的代码与序列化关系不大，可以不看
} catch (Throwable var10) {
if (writer != null) {
try {
((JSONWriter)writer).close();
} catch (Throwable var9) {
var10.addSuppressed(var9);
}
}
throw var10;
}
if (writer != null) {
((JSONWriter)writer).close();
}
return var12;
} catch (NumberFormatException | NullPointerException var11) {
throw new JSONException("JSON#toJSONString cannot serialize '" + object + "'", var11);
}
}
3.1.3 获取ObjectWriterProvider
JSON.toJSONString()入口：
JSONWriter.Context writeContext = new JSONWriter.Context(JSONFactory.defaultObjectWriterProvider);
其中会调用默认的构造方法初始化ObjectWriterProvider：
public ObjectWriterProvider() {
this.init();
ObjectWriterCreator creator = null;
switch (JSONFactory.CREATOR) {
case "reflect":
creator = ObjectWriterCreator.INSTANCE;
break;
case "lambda":
creator = ObjectWriterCreatorLambda.INSTANCE;
break;
case "asm":
default:
try {
creator = ObjectWriterCreatorASM.INSTANCE;
} catch (Throwable var5) {
}
if (creator == null) {
creator = ObjectWriterCreatorLambda.INSTANCE;
}
}
this.creator = (ObjectWriterCreator)creator;
}
ObjectWriterCreator采取的是单例模式，默认采用ASM动态字节码实现。
3.1.4 获取ObjectWriter
有了ObjectWriterProvider后，下一步就是获取ObjectWriter，也就是JSON.toJSONString()中的：
JSONWriter.Context context = ((JSONWriter)writer).context;
boolean fieldBased = (context.features & com.alibaba.fastjson2.JSONWriter.Feature.FieldBased.mask) != 0L;
ObjectWriter<?> objectWriter = context.provider.getObjectWriter(valueClass, valueClass, fieldBased);
getObjectWriter()如下：
public ObjectWriter getObjectWriter(Type objectType, Class objectClass, boolean fieldBased) {
// fieldBased是基于字段序列化的意思
// false的话表示基于getter序列化
// 根据不同的类型从不同的缓存map中获取
ObjectWriter objectWriter = fieldBased ? (ObjectWriter)this.cacheFieldBased.get(objectType) : (ObjectWriter)this.cache.get(objectType);
// 首次获取应该为null
if (objectWriter != null) {
return (ObjectWriter)objectWriter;
} else {
// 这个useModules布尔变量笔者不太了解
// 这里的逻辑是 基于字段反序列化 并且 目标class不为空 并且 目标class可以赋值给Iterable 并且 目标class不能赋值给class
boolean useModules = true;
if (fieldBased && objectClass != null && Iterable.class.isAssignableFrom(objectClass) && !Collection.class.isAssignableFrom(objectClass)) {
useModules = false;
}
// 这里的例子是true
if (useModules) {
for(int i = 0; i < this.modules.size(); ++i) {
// 获取ObjectWriterModule
ObjectWriterModule module = (ObjectWriterModule)this.modules.get(i);
objectWriter = module.getObjectWriter(objectType, objectClass);
// 为null
if (objectWriter != null) {
ObjectWriter previous = fieldBased ? (ObjectWriter)this.cacheFieldBased.putIfAbsent(objectType, objectWriter) : (ObjectWriter)this.cache.putIfAbsent(objectType, objectWriter);
if (previous != null) {
objectWriter = previous;
}
return (ObjectWriter)objectWriter;
}
}
}
// 第一次执行暂时还拿不到ObjectWriter，这里的条件全部符合
if (objectWriter == null && objectClass != null && !fieldBased) {
switch (objectClass.getName()) {
// 针对Guava库的map内置了ObjectWriter
case "com.google.common.collect.HashMultimap":
case "com.google.common.collect.LinkedListMultimap":
case "com.google.common.collect.LinkedHashMultimap":
case "com.google.common.collect.ArrayListMultimap":
case "com.google.common.collect.TreeMultimap":
objectWriter = GuavaSupport.createAsMapWriter(objectClass);
break;
// 不是JSONObject类
case "com.alibaba.fastjson.JSONObject":
objectWriter = ObjectWriterImplMap.of(objectClass);
}
}
// ObjectWriter还没拿到
if (objectWriter == null) {
// 第一次拿需要通过ObjectWriterCreator()去创建
ObjectWriterCreator creator = this.getCreator();
if (objectClass == null) {
objectClass = TypeUtils.getMapping(objectType);
}
// 创建ObjectWriter
// ObjectWriter的里面会创建FieldWriter，这里面的逻辑很长，经过一些列复杂逻辑的判断，再针对字段获取
objectWriter = creator.createObjectWriter(objectClass, fieldBased ? Feature.FieldBased.mask : 0L, this);
// 放入缓存
ObjectWriter previous = fieldBased ? (ObjectWriter)this.cacheFieldBased.putIfAbsent(objectType, objectWriter) : (ObjectWriter)this.cache.putIfAbsent(objectType, objectWriter);
if (previous != null) {
objectWriter = previous;
}
}
return (ObjectWriter)objectWriter;
}
}
其中FiledWriter获取逻辑如下：
// ObjectWriterCreatorASM.java 236行左右的位置
BeanUtils.fields(objectClass, (field) -> {
if (fieldBased || Modifier.isPublic(field.getModifiers())) {
fieldInfo.init();
// 创建FieldWriter
FieldWriter fieldWriter = this.creteFieldWriter(objectClass, writerFeatures, provider.modules, beanInfo, fieldInfo, field);
if (fieldWriter != null) {
// 放入缓存
fieldWriterMap.putIfAbsent(fieldWriter.fieldName, fieldWriter);
}
}
});
3.1.5 write()操作
获取到ObjectWriter之后，就可以进行write()操作了，JSON.toJSONString()入口：
objectWriter.write((JSONWriter)writer, object, (Object)null, (Type)null, 0L);
由于自定义类的ObjectWriter是运行时拿到的，无法通过调试获取到，但是可以通过内置的ObjectWriter来判断大概的write()流程：
比如LocalDateWriter的write()如下：
public void write(JSONWriter jsonWriter, Object object, Object fieldName, Type fieldType, long features) {
try {
int year = (Integer)this.getYear.invoke(object);
int monthOfYear = (Integer)this.getMonthOfYear.invoke(object);
int dayOfMonth = (Integer)this.getDayOfMonth.invoke(object);
Object chronology = this.getChronology.invoke(object);
if (chronology != this.utc && chronology != null) {
jsonWriter.startObject();
// 写入key
jsonWriter.writeName("year");
// 写入value
jsonWriter.writeInt32(year);
jsonWriter.writeName("month");
jsonWriter.writeInt32(monthOfYear);
jsonWriter.writeName("day");
jsonWriter.writeInt32(dayOfMonth);
jsonWriter.writeName("chronology");
jsonWriter.writeAny(chronology);
jsonWriter.endObject();
} else {
LocalDate localDate = LocalDate.of(year, monthOfYear, dayOfMonth);
DateTimeFormatter formatter = this.getDateFormatter();
if (formatter == null) {
formatter = jsonWriter.getContext().getDateFormatter();
}
if (formatter == null) {
jsonWriter.writeLocalDate(localDate);
} else {
String str = formatter.format(localDate);
jsonWriter.writeString(str);
}
}
} catch (InvocationTargetException | IllegalAccessException var14) {
throw new JSONException("write LocalDateWriter error", var14);
}
}
根据getter获取字段值并调用对应的Writer去写JSON。
3.2 反序列化
3.2.1 概览
反序列化也可以参考官方的一张图：
大概流程与序列化类似：
- 获取
ObjectReader - 如果
ObjectReaderProvider有缓存，从缓存提取 - 如果
ObjectReaderProvider没有缓存，创建ObjectReader并且缓存到ObjectReaderProvider中 - 通过
JSONReader得到Object - 返回结果
3.2.2 入口
Entity entity = Entity.builder().field1("a").field2(2).build();
String str = JSON.toJSONString(entity);
System.out.println(JSON.parseObject(str,Entity.class));
其中parseObject()如下：
static <T> T parseObject(String text, Class<T> clazz) {
if (text != null && !text.isEmpty()) {
// 获取JSONReader
JSONReader reader = JSONReader.of(text);
Object var7;
try {
JSONReader.Context context = reader.context;
// 判断是否基于字段反序列化
boolean fieldBased = (context.features & Feature.FieldBased.mask) != 0L;
// 通过ObjectReaderProvider获取ObjectReader
// 这个context看起来和ObjectReaderProvider无关，实际上内部实现Context包含了ObjectReaderProvider
ObjectReader<T> objectReader = context.provider.getObjectReader(clazz, fieldBased);
// 反序列化核心方法
T object = objectReader.readObject(reader, (Type)null, (Object)null, 0L);
if (reader.resolveTasks != null) {
reader.handleResolveTasks(object);
}
if (reader.ch != 26 && (reader.context.features & Feature.IgnoreCheckClose.mask) == 0L) {
throw new JSONException(reader.info("input not end"));
}
var7 = object;
} catch (Throwable var9) {
if (reader != null) {
try {
reader.close();
} catch (Throwable var8) {
var9.addSuppressed(var8);
}
}
throw var9;
}
if (reader != null) {
reader.close();
}
return var7;
} else {
return null;
}
}
3.2.3 获取JSONReader
JSON.parseObject()入口：
JSONReader reader = JSONReader.of(text);
其中JSONReader.of()实现如下：
public static JSONReader of(String str) {
if (str == null) {
throw new NullPointerException();
} else {
// 创建Context
// Context内部包含了ObjectReaderProvider
Context context = JSONFactory.createReadContext();
int length;
// 测试环境JDK8，此处if不成立
if (JDKUtils.JVM_VERSION > 8 && JDKUtils.UNSAFE_SUPPORT) {
try {
length = JDKUtils.STRING_CODER != null ? JDKUtils.STRING_CODER.applyAsInt(str) : UnsafeUtils.getStringCoder(str);
if (length == 0) {
byte[] bytes = JDKUtils.STRING_VALUE != null ? (byte[])JDKUtils.STRING_VALUE.apply(str) : UnsafeUtils.getStringValue(str);
return new JSONReaderASCII(context, str, bytes, 0, bytes.length);
}
} catch (Exception var4) {
throw new JSONException("unsafe get String.coder error");
}
}
length = str.length();
char[] chars;
// 测试环境JDK8
if (JDKUtils.JVM_VERSION == 8) {
// 获取char array
chars = JDKUtils.getCharArray(str);
} else {
chars = str.toCharArray();
}
// 由于JDK8的String还是使用char[]实现的，所以返回UTF16的JSONReader
return new JSONReaderUTF16(context, str, chars, 0, length);
}
}
3.2.4 获取ObjectReader
JSON.parseObject()入口：
ObjectReader<T> objectReader = context.provider.getObjectReader(clazz, fieldBased);
getObjectReader()如下：
public ObjectReader getObjectReader(Type objectType, boolean fieldBased) {
if (objectType == null) {
objectType = Object.class;
}
// 有缓存直接从缓存提取
ObjectReader objectReader = fieldBased ? (ObjectReader)this.cacheFieldBased.get(objectType) : (ObjectReader)this.cache.get(objectType);
// 第一次获取ObjectReader为null
if (objectReader != null) {
return objectReader;
} else {
Iterator var4 = this.modules.iterator();
ObjectReader previous;
while(var4.hasNext()) {
ObjectReaderModule module = (ObjectReaderModule)var4.next();
// 获取到的ObjectReader为null
objectReader = module.getObjectReader(this, (Type)objectType);
if (objectReader != null) {
previous = fieldBased ? (ObjectReader)this.cacheFieldBased.putIfAbsent(objectType, objectReader) : (ObjectReader)this.cache.putIfAbsent(objectType, objectReader);
if (previous != null) {
objectReader = previous;
}
return objectReader;
}
}
Type rawType;
// 条件不符合
if (objectType instanceof TypeVariable) {
Type[] bounds = ((TypeVariable)objectType).getBounds();
if (bounds.length > 0) {
rawType = bounds[0];
if (rawType instanceof Class) {
previous = this.getObjectReader(rawType, fieldBased);
if (previous != null) {
ObjectReader previous = this.getPreviousObjectReader(fieldBased, (Type)objectType, previous);
if (previous != null) {
previous = previous;
}
return previous;
}
}
}
}
// 条件不符合
if (objectType instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType)objectType;
rawType = parameterizedType.getRawType();
Type[] typeArguments = parameterizedType.getActualTypeArguments();
if (rawType instanceof Class) {
Class rawClass = (Class)rawType;
boolean generic = false;
for(Class clazz = rawClass; clazz != Object.class; clazz = clazz.getSuperclass()) {
if (clazz.getTypeParameters().length > 0) {
generic = true;
break;
}
}
if (typeArguments.length == 0 || !generic) {
ObjectReader rawClassReader = this.getObjectReader(rawClass, fieldBased);
if (rawClassReader != null) {
ObjectReader previous = this.getPreviousObjectReader(fieldBased, (Type)objectType, rawClassReader);
if (previous != null) {
rawClassReader = previous;
}
return rawClassReader;
}
}
}
}
Class<?> objectClass = TypeUtils.getMapping((Type)objectType);
String className = objectClass.getName();
if (objectReader == null && !fieldBased) {
switch (className) {
// 针对Guava的MultiMap，这里的条件不符合
case "com.google.common.collect.ArrayListMultimap":
objectReader = ObjectReaderImplMap.of((Type)null, objectClass, 0L);
}
}
// ObjectReader为null
if (objectReader == null) {
// 获取ObjectReaderCreator
ObjectReaderCreator creator = this.getCreator();
// 创建ObjectReader
objectReader = creator.createObjectReader(objectClass, (Type)objectType, fieldBased, this);
}
previous = this.getPreviousObjectReader(fieldBased, (Type)objectType, objectReader);
if (previous != null) {
objectReader = previous;
}
return objectReader;
}
}
在创建ObjectReader的同时，会在其中创建FieldReader：
// ObjectReaderCreator.java 453
FieldReader[] fieldReaderArray = this.createFieldReaders(objectClass, objectType, beanInfo, fieldBased, provider);
3.2.5 read()操作
有了ObjectReader之后就可以进行具体的read()操作了，JSON.parseObject()入口：
T object = objectReader.readObject(reader, (Type)null, (Object)null, 0L);
此处的readObject()如下：
// ObjectReaderNoneDefaultConstructor.java 171行
public T readObject(JSONReader jsonReader, Type fieldType, Object fieldName, long features) {
// 判断是否带有JSONReader.Feature.ErrorOnNoneSerializable
if (!this.serializable) {
jsonReader.errorOnNoneSerializable(this.objectClass);
}
// 是否JSONB，不符合
if (jsonReader.isJSONB()) {
return this.readJSONBObject(jsonReader, fieldType, fieldName, 0L);
} else if (jsonReader.isArray() && jsonReader.isSupportBeanArray(features | this.features)) {
// 是数组而且支持JSONReader.Feature.SupportArrayToBean，不符合
jsonReader.next();
LinkedHashMap<Long, Object> valueMap = null;
for(int i = 0; i < this.fieldReaders.length; ++i) {
Object fieldValue = this.fieldReaders[i].readFieldValue(jsonReader);
if (valueMap == null) {
valueMap = new LinkedHashMap();
}
long hash = this.fieldReaders[i].fieldNameHash;
valueMap.put(hash, fieldValue);
}
if (!jsonReader.nextIfMatch(']')) {
throw new JSONException(jsonReader.info("array not end, " + jsonReader.current()));
} else {
jsonReader.nextIfMatch(',');
return this.createInstanceNoneDefaultConstructor((Map)(valueMap == null ? Collections.emptyMap() : valueMap));
}
} else {
// 读取字符
boolean objectStart = jsonReader.nextIfObjectStart();
// 条件为false，进入else
if (!objectStart && !jsonReader.isTypeRedirect() && jsonReader.nextIfEmptyString()) {
return null;
} else {
// 获取Context，读取其中的Features
JSONReader.Context context = jsonReader.getContext();
long featuresAll = this.features | features | context.getFeatures();
// 此处存储对象的值
// key是字段的long哈希值，哈希采取的是fnv1a 64算法生成的
// value是字段的具体值
LinkedHashMap<Long, Object> valueMap = null;
// 读取
for(int i = 0; !jsonReader.nextIfMatch('}'); ++i) {
// 读取字段名对应的hashCode
long hashCode = jsonReader.readFieldNameHashCode();
if (hashCode != 0L) {
if (hashCode == this.typeKeyHashCode && i == 0) {
long typeHash = jsonReader.readTypeHashCode();
// 此处if条件不符合
if (typeHash != this.typeNameHash) {
boolean supportAutoType = (featuresAll & Feature.SupportAutoType.mask) != 0L;
ObjectReader autoTypeObjectReader;
String typeName;
if (supportAutoType) {
autoTypeObjectReader = context.getObjectReaderAutoType(typeHash);
if (autoTypeObjectReader == null) {
typeName = jsonReader.getString();
autoTypeObjectReader = context.getObjectReaderAutoType(typeName, this.objectClass, this.features);
}
} else {
typeName = jsonReader.getString();
autoTypeObjectReader = context.getObjectReaderAutoType(typeName, this.objectClass);
}
if (autoTypeObjectReader == null) {
typeName = jsonReader.getString();
autoTypeObjectReader = context.getObjectReaderAutoType(typeName, this.objectClass, this.features);
}
if (autoTypeObjectReader != null) {
Object object = autoTypeObjectReader.readObject(jsonReader, fieldType, fieldName, 0L);
jsonReader.nextIfMatch(',');
return object;
}
}
} else {
// 获取字段名哈希对应的FieldReader
FieldReader fieldReader = this.getFieldReader(hashCode);
// 条件不符合
if (fieldReader == null && (featuresAll & Feature.SupportSmartMatch.mask) != 0L) {
long hashCodeLCase = jsonReader.getNameHashCodeLCase();
if (hashCodeLCase != hashCode) {
fieldReader = this.getFieldReaderLCase(hashCodeLCase);
}
}
// fieldReader不为null
if (fieldReader == null) {
this.processExtra(jsonReader, (Object)null);
} else {
// 读取字段值
Object fieldValue = fieldReader.readFieldValue(jsonReader);
if (valueMap == null) {
valueMap = new LinkedHashMap();
}
long hash;
if (fieldReader instanceof FieldReaderObjectParam) {
hash = ((FieldReaderObjectParam)fieldReader).paramNameHash;
} else {
hash = fieldReader.fieldNameHash;
}
// 写入
valueMap.put(hash, fieldValue);
}
}
}
}
// 构造对象
T object = this.createInstanceNoneDefaultConstructor((Map)(valueMap == null ? Collections.emptyMap() : valueMap));
if (this.setterFieldReaders != null && valueMap != null) {
for(int i = 0; i < this.setterFieldReaders.length; ++i) {
FieldReader fieldReader = this.setterFieldReaders[i];
// 读取字段值
Object fieldValue = valueMap.get(fieldReader.fieldNameHash);
if (fieldValue != null) {
// 通过setter注入
fieldReader.accept(object, fieldValue);
}
}
}
jsonReader.nextIfMatch(',');
return object;
}
}
}
4 结尾
其实文章中很多细节的地方由于篇幅的限制无法过于详细的解释，比如内置的各类型的Reader/Writer具体是如何获取值进行序列化/反序列操作的，想要深入探究这部分就只能自己去挖源码了。另外需要注意的是，文章的环境是在JDK8下的，由于Fastjson2在不同的JDK下会有不同的序列化实现，因此仅供参考。
最后，关于性能的比较，可以参考官方的比较基准。
5 参考
- Fastjson2 Github
- Fastjson2 Wiki