jsonson GetStarted

1、 home page

Jackson home page

jackson: JSON library for java

java对象序列化和json字符串反序列化工具；

json字符串反序列化生成Java对象， 支持各种类型的数据类型绑定， 支持基本数据类型及其包装类， String类型， 时间类型， 数组、集合类型等；

databind
ObjectMapper注册类型映射器；
ObjectMapper / ObjectReader / ObjectWriter

JsonFactory

ObjectCodec
codec编解码器
Object that implements conversion functionality between Java objects and JSON content.

ObjectMapper extends ObjectCodec

JsonParser
defines public API for reading JSON content.
读取json content;
由JsonFactory创建；

JsonGenerator 序列化pojos
defines public API for writing JSON content.
生成一个json content;
由JsonFactory创建；

一个JsonFactory包括：
ObjectMapper
JSONPaser
JSONGenerator

关注点应该在databind

2、jackson-docs

jackson-docs

Jackson Core: Streaming: JsonFactory.Feature; JsonParser.Feature; JsonGenerator.Feature

Jackson Annotations: This page lists all general-purpose Jackson 2.0 annotations, grouped by functionality.

易百教程

3、api

  final ObjectMapper mapper = new ObjectMapper(); // can use static singleton, inject: just make sure to reuse!
  MyValue value = new MyValue();
  // ... and configure
  File newState = new File("my-stuff.json");
  mapper.writeValue(newState, value); // writes JSON serialization of MyValue instance
  // or, read
  MyValue older = mapper.readValue(new File("my-older-stuff.json"), MyValue.class);

  // Or if you prefer JSON Tree representation:
  JsonNode root = mapper.readTree(newState);
  // and find values by, for example, using a {@link com.fasterxml.jackson.core.JsonPointer} expression:
  int age = root.at("/personal/age").getValueAsInt(); 

4、 databind

日期、枚举自定义转换

在ObjectMapper中定义module; 指定字段类型的序列化和反序列化；

 /**
     * Method for registering a module that can extend functionality
     * provided by this mapper; for example, by adding providers for
     * custom serializers and deserializers.
     * 
     * @param module Module to register
     */
    public ObjectMapper registerModule(Module module)
    {
        if (isEnabled(MapperFeature.IGNORE_DUPLICATE_MODULE_REGISTRATIONS)) {
            Object typeId = module.getTypeId();
            if (typeId != null) {
                if (_registeredModuleTypes == null) {
                    // plus let's keep them in order too, easier to debug or expose
                    // in registration order if that matter
                    _registeredModuleTypes = new LinkedHashSet<Object>();
                }
                // try adding; if already had it, should skip
                if (!_registeredModuleTypes.add(typeId)) {
                    return this;
                }
            }
        }
        
   

5、注解