JsonUtil

序列化和反序列化工具类

 <dependency>
      <groupId>org.codehaus.jackson</groupId>
      <artifactId>jackson-mapper-asl</artifactId>
      <version>1.9.12</version>
    </dependency>

package com.mark.util;

import com.google.common.collect.Lists;
import com.mark.pojo.User;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.codehaus.jackson.map.annotate.JsonSerialize;
import org.codehaus.jackson.type.JavaType;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.List;

/**
 * Created by Mark on 2018/4/20.
 * Json序列化工具类
 */

@Slf4j
public class JsonUtil {
    private static ObjectMapper objectMapper = new ObjectMapper();
    static {
        //对象的所有字段全部列入
        objectMapper.setSerializationInclusion(JsonSerialize.Inclusion.ALWAYS);

        //取消默认转换timestamps形式
        objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

        //忽略空Bean转json的错误
        objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

        //所有的日期格式都统一为以下的样式，即yyyy-MM-dd HH:mm:ss
        objectMapper.setDateFormat(new SimpleDateFormat(DateTimeUtil.STANDARD_FORMAT));

        //反序列化属性：忽略在json字符串中存在，但是在java对象中不存在对应属性的情况。防止错误
        objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
    }

    //1.对象转为字符串
    public static <T> String obj2String(T obj){
        if(obj == null){
            return null;
        }
        try {
            //如果传入的对象是字符串类型就直接返回否则才进行序列化
            return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
        } catch (Exception e) {
            log.warn("Parse Object to String error",e);
            return null;
        }
    }

    //2.对象装字符串2【带有格式】
    public static <T> String obj2StringPretty(T obj){
        if (obj == null){
            return null;
        }
        try {
            return obj instanceof String ? (String)obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
        } catch (Exception e) {
            log.warn("Parse Object to String error",e);
            return null;
        }
    }

    //3.字符串反序列话为普通对象
    public static <T> T string2Obj(String str,Class<T> clazz){
        if(StringUtils.isEmpty(str) || clazz == null){
            return null;
        }
        try {
            //如果需要转为String类型就直接返回，否则才进行转换
            return clazz.equals(String.class) ? (T) str :objectMapper.readValue(str,clazz);
        } catch (IOException e) {
            log.warn("Parse String to Object error",e);
            return null;
        }
    }

    //字符串反序列化为集合1
    public static <T> T string2Obj(String str, TypeReference<T> typeReference){
        if(StringUtils.isEmpty(str) || typeReference == null){
            return null;
        }
        try {
            return (T)(typeReference.getType().equals(String.class)? str : objectMapper.readValue(str,typeReference));
        } catch (Exception e) {
            log.warn("Parse String to Object error",e);
            return null;
        }
    }

    //字符串反序列化为集合2
    public static <T> T string2Obj(String str,Class<?> collectionClass,Class<?>... elementClasses){
        JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses);
        try {
            return objectMapper.readValue(str,javaType);
        } catch (Exception e) {
            log.warn("Parse String to Object error",e);
            return null;
        }
    }


    //测试
    public static void main(String[] args) {
       /* User user1 = new User();
        user1.setId(1);
        user1.setUsername("mark");
        String user1Json = JsonUtil.obj2String(user1);//对象序列化
        String user1JsonPretty = JsonUtil.obj2StringPretty(user1);//对象序列化
        System.out.println(user1Json);
        System.out.println(user1JsonPretty);

        User user = JsonUtil.string2Obj(user1Json,User.class);
        System.out.println(user.getId());*/

        User user1 = new User();
        user1.setId(1);
        user1.setUsername("mark");
        User user2 = new User();
        user2.setId(1);
        user2.setUsername("mark");

        List<User> userList = Lists.newArrayList();
        userList.add(user1);
        userList.add(user2);
        String result = JsonUtil.obj2StringPretty(userList);//集合序列化为字符串
        System.out.println(result);
        List<User> userList1 = JsonUtil.string2Obj(result, new TypeReference<List<User>>() {
        });
        List<User> userList2 = JsonUtil.string2Obj(result,List.class,User.class);
        System.out.println("end");

    }



}