json与Java对象 转换的几种方法

package com.yoyohr.bi.bean;import com.fasterxml.jackson.core.JsonGenerationException;import com.fasterxml.jackson.core.JsonParseException;import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.type.TypeReference;import com.fasterxml.jackson.databind.*;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.io.IOException;import java.util.ArrayList;import java.util.List;import static mondrian.server.MondrianServerRegistry.logger;/** * Created by Administrator on 2017/2/18. */public class Test {    private static String jsonUser ="{\"id\":1,\"name\":\"kexianqin\"}";    private static String jsonUserArray ="[{\"id\":1,\"name\":\"kexianqin\"},{\"id\":2,\"name\":\"liuchen\"}]";    private final static ObjectMapper objectMapper = new ObjectMapper();    private static final Logger logger = LoggerFactory.getLogger(Test.class);    public static void main(String[] args) throws IOException {        logger.info("Test begin........");         /**         使用JavaType方法          *///        JavaType javaType = objectMapper.getTypeFactory().constructCollectionType(ArrayList.class,UserT.class);//        List<UserT> userList = objectMapper.readValue(jsonUserArray,javaType);//        System.out.println(userList);        /**         TypeReference：可以把json字符串转换成想要的List.        注意readValue()方法里的new TypeReference<List<UserT>>() { }写法很关键，写成List.class是不行的，         *///         List<UserT> userlist = objectMapper.readValue(jsonUserArray,new TypeReference<List<UserT>>(){});// 若无toString方法：[com.yoyohr.bi.bean.UserT@58651fd0, com.yoyohr.bi.bean.UserT@4520ebad]//         List userlist2 = objectMapper.readValue(jsonUserArray,new TypeReference<List>() { });// [{id=1, name=kexianqin}, {id=2, name=liuchen}]//         System.out.println(userlist);//         System.out.println(userlist2);        /**         最普通的         *///        UserT user=objectMapper.readValue(jsonUser,UserT.class);//json转化为UserT类对象//        System.out.print(user.toString());//        String jsonString=objectMapper.writeValueAsString(user);//对象转化为json//        System.out.println(jsonString);        /**            类中含类，如cube中包含多个dimension,:{"users":[{"id":3,"name":"kxq"},{"id":4,"name":"lc"}],"dname":"体育经济Q1241"}         *///        UserT user1 = new UserT();//        user1.setId(3);//        user1.setName("kxq");////        UserT user2 = new UserT();//        user2.setId(4);//        user2.setName("lc");////        Department class1=new Department();//        class1.setDname("体育经济Q1241");//        List<UserT> listUser=new ArrayList();//        listUser.add(user1); listUser.add(user2);//        class1.setUsers(listUser);////        String jsonString = objectMapper.writeValueAsString(class1);//        System.out.println(jsonString);        /**         * 调用下面的方法<即最终方法>         */        System.out.println(decode(jsonUser,UserT.class));        System.out.println(decode(jsonUserArray,new TypeReference<List<UserT>>(){}));//！！！！！！！！！！！！！{ }是干什么用的？？  <T>与<?>    }    /**     * 将对象序列化     * @param obj     * @return     */    public static String encode(Object obj) {        try {            return objectMapper.writeValueAsString(obj);        } catch (JsonGenerationException e) {            logger.error("encode(Object)", e); //$NON-NLS-1$        } catch (JsonMappingException e) {            logger.error("encode(Object)", e); //$NON-NLS-1$        } catch (IOException e) {            logger.error("encode(Object)", e); //$NON-NLS-1$        }        return null;    }    /**     * 将json string反序列化成对象     *     * @param json     * @param valueType     * @return     */    public static <T> T decode(String json, Class<T> valueType ) {        try {            return objectMapper.readValue(json, valueType);        } catch (JsonParseException e) {            logger.error("decode(String, Department<T>)", e);        } catch (JsonMappingException e) {            logger.error("decode(String, Department<T>)", e);        } catch (IOException e) {            logger.error("decode(String, Department<T>)", e);        }        return null;    }    /**     * 将json array反序列化为对象     *     * @param json     * @param jsonTypeReference     * @return     */    public static <T> T decode(String json, TypeReference<T> jsonTypeReference) {        try {            return (T) objectMapper.readValue(json, jsonTypeReference);        } catch (JsonParseException e) {            logger.error("decode(String, JsonTypeReference<T>)", e);        } catch (JsonMappingException e) {            logger.error("decode(String, JsonTypeReference<T>)", e);        } catch (IOException e) {            logger.error("decode(String, JsonTypeReference<T>)", e);        }        return null;    }}