Jackson工具，java对象和json字符串之间的互相转换

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一、maven依赖引入jackson

		<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.12.5</version></dependency>

jackson-databind依赖见下：

    <dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId></dependency>

二、JsonUtil工具类

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;public class JsonUtil {public static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();/*** Json encode** @param object object* @return String*/public static String encode(Object object) {try {return OBJECT_MAPPER.writeValueAsString(object);} catch (JsonProcessingException e) {throw new RuntimeException("Json encode failed!", e);}}/*** Json decode** @param json          json* @param typeReference typeReference* @param <T>           T* @return T*/public static <T> T decode(String json, TypeReference<T> typeReference) {try {return OBJECT_MAPPER.readValue(json, typeReference);} catch (Exception e) {throw new RuntimeException("Json decode failed!", e);}}/*** Json decode** @param json        json* @param targetClass targetClass* @param <T>         T* @return T*/public static <T> T decode(String json, Class<T> targetClass) {try {return OBJECT_MAPPER.readValue(json, targetClass);} catch (Exception e) {throw new RuntimeException("Json decode failed!", e);}}
}

三、使用示例

定义一个User对象

    @AllArgsConstructor@NoArgsConstructor@Datapublic static class User {private String name;private Integer age;}

• encode() 单个对象

String str = JsonUtil.encode(new User("张三", 10));// {"name":"张三","age":10}
System.out.println(str);

• encode() 对象集合

   List<User> userList  = Lists.newArrayList();userList.add(new User("张三", 10));userList.add(new User("李四", 12));String str = JsonUtil.encode(userList);// [{"name":"张三","age":10},{"name":"李四","age":12}]System.out.println(str);    

• decode() 单个对象

   String json = "{\"name\":\"stelin\",\"age\":18}";User user = JsonUtil.decode(json, User.class);// JsonUtil.User(name=stelin, age=18)System.out.println(user);

• decode() 对象集合

String str = "[{\"name\":\"张三\",\"age\":10},{\"name\":\"李四\",\"age\":12}]";List<User> userList = JsonUtil.decode(str, new TypeReference<List<User>>() {});// [JsonUtil.User(name=张三, age=10), JsonUtil.User(name=李四, age=12)]
System.out.println(userList);

• decode() 字符串集合

String str = "[1, 2, 3]";List<String> list = JsonUtil.decode(str, new TypeReference<List<String>>() {
});// [1, 2, 3]
System.out.println(list);

很多jar包都会有类TypeReference，别错误地引用了，注意这里的TypeReference是com.fasterxml.jackson.core.type.TypeReference。

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