这篇文章主要介绍“jackson怎么通用反序列化组件”，在日常操作中，相信很多人在jackson怎么通用反序列化组件问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”jackson怎么通用反序列化组件”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
Java生态圈中有很多处理JSON和XML格式化的类库,Jackson是其中比较著名的一个</br> 官址:https://github.com/FasterXML<br> Jackson提供了Jackson-databind来操控JSON处理,提供了比较丰富的API,和入门指南<br> 文档:https://github.com/FasterXML/jackson-databind <br> JAVA是一种灵活性,扩展性比较强的语言,继承,实现,范型,多态等都是很好的体现,Jackson-databind作为JAVA生态圈的类库,当然会对这些特性有对应的实现,具体可以在官方指导文档中,或者是在指导测试中找到相关的介绍。
你会发现官方给出的基本上都是基于单个Bean的,或者是某一类型的定制方案。官方暂未提供通用的解决方案,
对于有些基于JSON数据传输的系统,通过JACKSON进行BEAN的反序列化时,如果没有定制Deserializer行为,Jackson默认的BeanDeserializer,此时需要明确此Bean类结构,Bean中的属性类型,枚举以及嵌套类(内部类)中必须显式包含'无参构造器'(NON-DEFAULT CONSTRUCTOR),否则反序列化会失败,具体异常描述"No suitable constructor found for type [XXXX]"
针对上述的2个问题，jackson-ext-beanInstantiation提供解决方案,并且提供基于jackson-databind simple module的集成方案 具体代码参考：https://github.com/dylan1108/jackson-ext-beanInstantiation
Bean序列化时,对于含有多态类型的引用,将此引用的具体实例对象类的信息作为辅助信息,以Key-Value的方式保存到JNode中 Bean反序列化时,会根据JNode中的引用类型的类的辅助信息,来决定使用具体的类来进行反序列化绑定。
JVM unsafe mechanism机制无需依赖构造器的方式实例化对象,然后在对Bean对象进行属性设置
public class UnsafeAllocator {
private static Unsafe unsafe;
static{
try {
Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
Field f = unsafeClass.getDeclaredField("theUnsafe");
f.setAccessible(true);
unsafe = (Unsafe) f.get(null);
} catch (Exception ignored) {
ignored.printStackTrace();
}
}
public static Object beanAllocatorByJvmUnsafe(Class<?> clazz) throws InstantiationException {
if(unsafe==null){
throw new InstantiationException(String.format("Jvm Unsafe could't find,Make sure load unsafe security in [%s]",clazz.getName()));
}
return unsafe.allocateInstance(clazz);
}
}@Override
public Object deserializeFromObjectUsingNonDefault(JsonParser p,DeserializationContext ctxt) throws IOException{
JsonDeserializer<Object> delegateDeser = _delegateDeserializer;
if (delegateDeser == null) {
delegateDeser = _arrayDelegateDeserializer;
}
if (delegateDeser != null) {
return _valueInstantiator.createUsingDelegate(ctxt,
delegateDeser.deserialize(p, ctxt));
}
if (_propertyBasedCreator != null) {
return _deserializeUsingPropertyBased(p, ctxt);
}
/*
// 25-Jan-2017, tatu: We do not actually support use of Creators for non-static
// inner classes -- with one and only one exception; that of default constructor!
// -- so let's indicate it
//=== Unsafe Allocator support Bean instantiate with Non default creator,Include the non-static inner class =====
Class<?> raw = _beanType.getRawClass();
if (ClassUtil.isNonStaticInnerClass(raw)) {
return ctxt.handleMissingInstantiator(raw, null, p,
"can only instantiate non-static inner class by using default, no-argument constructor");
}*/
return _deserializeNonDefaultWithUnsafeAllocator(p,ctxt);
}
private void fillBeanFieldValue(JsonParser p, DeserializationContext ctxt, Object bean) throws IOException {
p.setCurrentValue(bean);
if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)) {
String propName = p.getCurrentName();
do {
p.nextToken();
SettableBeanProperty prop = _beanProperties.find(propName);
if (prop != null) { // normal case
try {
prop.deserializeAndSet(p, ctxt, bean);
} catch (Exception e) {
wrapAndThrow(e, bean, propName, ctxt);
}
continue;
}
handleUnknownVanilla(p, ctxt, bean, propName);
} while ((propName = p.nextFieldName()) != null);
}
}public class MyBeanDeserializerModifier extends BeanDeserializerModifier {
@Override
public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config, BeanDescription beanDesc, JsonDeserializer<?> deserializer) {
//replace default BeanDeserializer to support instantiate bean with Non-default creator.
if (deserializer instanceof BeanDeserializer) {
return new MyBeanDeserializer((BeanDeserializer) deserializer);
}
return deserializer;
}
}{
"@class": "com.jackson.ext.test.vo.MockBizDataContext",
"bizDataMap": {
"@class": "java.util.HashMap",
"{\"@class\":\"java.lang.String\",\"value\":\"MockPojoWithNonDefaultConstructorList\"}": ["java.util.ArrayList", [{
"@class": "com.jackson.ext.test.vo.MockPojoWithNonDefaultConstructor",
"poiId": 123,
"comment": "test1",
"userName": "yilami1",
"phone": "11111111"
}, {
"@class": "com.jackson.ext.test.vo.MockPojoWithNonDefaultConstructor",
"poiId": 234,
"comment": "test2",
"userName": "yilami2",
"phone": "22222222"
}]],
"{\"@class\":\"java.lang.String\",\"value\":\"MockPojoWithNonStaticInnerPojo_Outer\"}": {
"@class": "com.jackson.ext.test.vo.MockPojoWithNonStaticInnerPojo_Outer",
"outerName": "Outer[1]",
"mockPojoWithNonStaticInnerPojo_inner": {
"@class": "com.jackson.ext.test.vo.MockPojoWithNonStaticInnerPojo_Outer$MockPojoWithNonStaticInnerPojo_Inner",
"innerName": "Inner[1]"
}
},
"{\"@class\":\"java.lang.String\",\"value\":\"createTime\"}": ["java.util.Date", 1576838321729],
"{\"@class\":\"java.lang.String\",\"value\":\"MockPojoWithNonDefaultConstructor1\"}": {
"@class": "com.jackson.ext.test.vo.MockPojoWithNonDefaultConstructor",
"poiId": 123,
"comment": "test1",
"userName": "yilami1",
"phone": "11111111"
},
"{\"@class\":\"java.lang.String\",\"value\":\"MockPojoWithNonDefaultConstructor2\"}": {
"@class": "com.jackson.ext.test.vo.MockPojoWithNonDefaultConstructor",
"poiId": 234,
"comment": "test2",
"userName": "yilami2",
"phone": "22222222"
},
"{\"@class\":\"java.lang.String\",\"value\":\"MockEnumWithNonDefaultCreator\"}": ["com.jackson.ext.test.Enum.MockEnumWithNonDefaultCreator", "NO"],
"{\"@class\":\"java.lang.String\",\"value\":\"MockPojoWithNonStaticInnerPojo_Inner\"}": {
"@class": "java.lang.Object",
"innerName": "Inner[1]"
}
}
}<properties>
...
<!-- Use the latest version whenever possible. -->
<jackson.version>2.10.0</jackson.version>
...
</properties>
<dependencies>
...
<dependency>
<groupId>com.jackson.ext</groupId>
<artifactId>jackson-ext-beanInstantiation</artifactId>
<version>${jackson.version}</version>
</dependency>
...
</dependencies>使用Maven编译和打包jackson-ext-beanInstantiation之后，使用Jackson_Enhance_Utils会提供想对应的序列化和反序列化接口即可
sun.misc.Unsafe的JDK版本的支持
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