json和java对象相互转换

springboot中json转换默认使用的是jackson包，通过spring-boot-starter-web依赖的

1 在属性上添加注解@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")

　　可以修改对象转成json后的时间格式

2 在属性上添加注解 @JsonInclude(JsonInclude.Include.NON_NULL)

　　如果该属性为null,则不序列化

       Include.Include.ALWAYS 默认 
       Include.NON_DEFAULT 属性为默认值不序列化 
       Include.NON_EMPTY 属性为 空（""） 或者为 NULL 都不序列化 
       Include.NON_NULL 属性为NULL 不序列化

3  在属性上添加注解 @JsonProperty("userName")

 　这里的别名'userName' ,可以有两个作用

     一，当对象转为json时，该属性的key就是别名。

     二，当json转为对象时，像这种格式{"id":100,"phone":"15211115013","name.wx":"zs"}  , "name,wx" 就要为属性设置别名，否则转换会出错

 4 在属性上添加注解@JsonIgnore 会忽略该属性，不会向前台返回该属性

import java.io.IOException;
import java.util.List;
import java.util.Map;

import org.springframework.lang.Nullable;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonUtils {
 
    public static final ObjectMapper mapper = new ObjectMapper();

    /**
     * 对象转换为json字符串
     * @param obj
     * @return
     */
    @Nullable
    public static String toString(Object obj) {
        if (obj == null) {
            return null;
        }
        if (obj.getClass() == String.class) {
            return (String) obj;
        }
        try {
            return mapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            return null;
        }
    }
 
    @Nullable
    public static <T> T toBean(String json, Class<T> tClass) {
        try {
            return mapper.readValue(json, tClass);
        } catch (IOException e) {
            return null;
        }
    }
 
    @Nullable
    public static <E> List<E> toList(String json, Class<E> eClass) {
        try {
            return mapper.readValue(json, mapper.getTypeFactory().constructCollectionType(List.class, eClass));
        } catch (IOException e) {
            
            return null;
        }
    }
 
    @Nullable
    public static <K, V> Map<K, V> toMap(String json, Class<K> kClass, Class<V> vClass) {
        try {
            return mapper.readValue(json, mapper.getTypeFactory().constructMapType(Map.class, kClass, vClass));
        } catch (IOException e) {
            return null;
        }
    }
 
    @Nullable
    public static <T> T nativeRead(String json, TypeReference<T> type) {
        try {
            return mapper.readValue(json, type);
        } catch (IOException e) {
            return null;
        }
    }

   class User{
        private String name;
        private Integer age;
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public Integer getAge() {
            return age;
        }
        public void setAge(Integer age) {
            this.age = age;
        }
        public User() {
            super();
        }
    }
   
    public static void main(String[] args) {
        String json="{"namge":"zhuxinjun","age":"21"}";
        Map<String, String> map = toMap(json, String.class, String.class);
        System.out.println("map:"+map);
        
        String j="[{"namge":"zhuxinjun","age":"21"},{"namge":"yangyang","age":"32"}]";
        List<Map<String, String>> maps = nativeRead(j, new TypeReference<List<Map<String, String>>>() {
        });
        for(Map<String,String> map1:maps){
            System.out.println("map1"+map1);
        }
    }

}

 转载自： https://blog.csdn.net/u013089490/article/details/83585794