1. 入门案例
package com.test;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.ObjectMapper;import com.jt.pojo.ItemDesc;import org.junit.jupiter.api.Test;import java.util.ArrayList;import java.util.Date;import java.util.List;public class TestObjectMapper { /** * 1.通过测试类 实现对象与JSON之间的转化 * 重点常识: * 1.对象转化JSON 获取所有的getXXX()办法~~~~去除get~~~~~首字母小写~~造成属性 * 2.JSON转化为对象 利用Class的反射机制实例化对象~~~~获取json中的属性 * ~~~~拼接setXXX办法~~~~~调用对象的setXXX(arg)办法为对象赋值 */ @Test public void test01() throws JsonProcessingException { ItemDesc itemDesc = new ItemDesc(); itemDesc.setItemId(100L).setItemDesc("转化测试").setCreated(new Date()); ObjectMapper objectMapper = new ObjectMapper(); //1.将对象转化为JSON String json = objectMapper.writeValueAsString(itemDesc); System.out.println(json); //2.将JSON转化为对象 反射思维 ItemDesc itemDesc2 = objectMapper.readValue(json, ItemDesc.class); System.out.println(itemDesc2.getCreated()); } // 汇合 转 json @Test public void testList() throws JsonProcessingException { List<ItemDesc> list = new ArrayList<>(); list.add(new ItemDesc().setItemId(100L).setItemDesc("案例1")); list.add(new ItemDesc().setItemId(100L).setItemDesc("案例1")); ObjectMapper objectMapper = new ObjectMapper(); String json = objectMapper.writeValueAsString(list); System.out.println(json); List list2 = objectMapper.readValue(json, list.getClass()); System.out.println(list2); }}
2. 封装ObjectMapperUtil
package com.util;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.ObjectMapper;import com.jt.pojo.ItemDesc;public class ObjectMapperUtil { private static final ObjectMapper MAPPER = new ObjectMapper(); //1.对象转化为JSON public static String toJSON(Object obj){ try { return MAPPER.writeValueAsString(obj); } catch (JsonProcessingException e) { //将查看异样.转化为运行时异样 之后被全局异样解决机制解决 e.printStackTrace(); //日志打印.... throw new RuntimeException(e);// 抛出运行时异样，交给本人写好的全局异样解决 } } //2.JSON转化为对象 用户指定什么样的类型,返回什么样的对象???? // 传什么就返回什么---用泛型来实现 <T> 示意定义泛型，java中先定义，后应用 public static <T> T toObj(String json,Class<T> target){ try { return MAPPER.readValue(json, target); } catch (JsonProcessingException e) { e.printStackTrace(); throw new RuntimeException(e); } }}