Jackson對泛型的序列化和反序列化方法彙總

說明：Jackson對于簡單泛型是可以正常操作的，但是如果對于太過于複雜的泛型類有時會不成功。目前還在找着更合适的Json庫。不過這一點在dotnet原生方案JavaScriptSerializer可以完美解決這一些問題，無論泛型多複雜。

例子如下：

package com.jsoft.springboottest.springboottest1.controller;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.jsoft.springboottest.springboottest1.Pager;
import com.jsoft.springboottest.springboottest1.PagerAppoint;
import com.jsoft.springboottest.springboottest1.User;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl;

@RestController
public class TestController {

    private static final Logger logger = LoggerFactory.getLogger(TestController.class);

    @RequestMapping("/show")
    public String show() throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        User user = new User();
        user.setId(1);
        Pager<User> pager = new Pager<User>();
        List<User> users = new ArrayList<User>();
        users.add(user);
        pager.setDatas(users);
        String json = mapper.writeValueAsString(pager);
        // 方式1
        Pager<User> userPager1 = mapper.readValue(json, new TypeReference<Pager<User>>() {
        });
        // 方式2
        Type[] types = new Type[1];
        types[0] = User.class;
        final ParameterizedTypeImpl type = ParameterizedTypeImpl.make(Pager.class, types, Pager.class.getDeclaringClass());
        TypeReference typeReference = new TypeReference<Pager>() {
            @Override
            public Type getType() {
                return type;
            }
        };
        Pager<User> userPager2 = mapper.readValue(json, typeReference);
        // 方式3
        JavaType javaType = mapper.getTypeFactory().constructParametrizedType(Pager.class, Pager.class, User.class);
        Pager<User> userPager3 = mapper.readValue(json, javaType);
        // 方式4
        JavaType javaType1 = mapper.getTypeFactory().constructParametricType(Pager.class, User.class);
        Pager<User> userPager4 = mapper.readValue(json, javaType1);
        // 方式5，建立另一個指定具體泛型T的參數的類
        PagerAppoint userPager5 = mapper.readValue(json, PagerAppoint.class);
        // 數組泛型的序列化和反序列化
        String json1 = mapper.writeValueAsString(users);
        JavaType javaType2 = mapper.getTypeFactory().constructParametricType(List.class, User.class);
        List<User> users1 = mapper.readValue(json1, javaType2);
        // HashMap
        Map<String, User> map = new HashMap<String, User>(16);
        map.put("test", user);
        String json2 = mapper.writeValueAsString(map);
        // 1
        Map<String, User> users2 = mapper.readValue(json2, new TypeReference<Map<String, User>>() {
        });
        // 2
        JavaType javaType3 = mapper.getTypeFactory().constructParametricType(HashMap.class, String.class, User.class);
        Map<String, User> users3 = mapper.readValue(json2, javaType3);

        return "hello world";
    }
}      

示例工程：​​https://github.com/easonjim/5_java_example/tree/master/springboottest/springboottest10​​

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