Com alibaba. Common methods of fastjson

Fastjson It's a Java library , Can be Java Object to JSON Format , Of course, it can also make JSON String conversion to Java object .

Provides toJSONString() and parseObject() Methods to Java Object and the JSON transformation . call toJSONString Fang Method to convert an object to JSON character string ,parseObject The method is reversed JSON Converts a string to an object .

Create a User object , Attributes are id,name,age,address,is_del,create_time,update_time wait

User user = new User();
user.setAddress("A1");
user.setAge(11);
user.setCreate_time(new Date());
user.setName("monishan");

1. call toJSONString Fang Method to convert an object to JSON character string

String result = toJSONStringIgnoreNullValue(user );

The output is ：

{"address":"A1","age":11,"create_time":1623999789993,"name":"monishan"}

Some attribute values are null, Turn into JSON String will be ignored

add SerializerFeature.WriteMapNullValue That is to say value The value is null No display

String result = toJSONStringContainNullValue(object, SerializerFeature.WriteMapNullValue);

The output is ：

{"address":"A1","age":11,"create_time":1623999789000,"del_time":null,"id":null,"is_del":null,"name":"monishan","update_time":null}

Some attributes need to be formatted , Or change value

String result = toJSONStringValueFilter(object);

Defining classes SimpleValueFilter, Realization ValueFilter Interface

public class SimpleValueFilter implements ValueFilter {

	@Override
	public Object process(Object object, String name, Object value) {
		if (null == value) {
			return "";//value The value is null Set to empty string 
		}
		if ("name".equals(name)) {
			return "***" + value + "***";
		}
		
		if ("create_time".equals(name)) {// Date formatting 
			return CommonUtils.dateFormat((Date)value, null);
		}
		return value;
	}

}

The output is ：

{"address":"A1","age":11,"create_time":"2021-06-18 15:03:09","del_time":"","id":"","is_del":"","name":"***monishan***","update_time":""}

2. take JSON String conversion to Java object

take json String to User user

User entity = toEntity(value, User.class);

take json String to List<User> userList

List<User> userList = toObject(value,  new com.alibaba.fastjson.TypeReference<List<User>>() {});

[{"address":"A1","age":11,"create_time":1624003599005,"del_time":null,"id":null,"is_del":null,"name":"monishan","update_time":null}]

Encapsulation method ：

    /***
     * <p>Title: toObject</p>  
     * <p>Description:  take json Convert string to object of specified type , Use TypeReference You can explicitly specify the type of deserialization </p>  
     * @param <T>
     * @param value
     * @param typeReference
     * @return
     */
    public static <T> T toObject(String value, com.alibaba.fastjson.TypeReference<T> typeReference) {
		return JSONObject.parseObject(value, typeReference, Feature.values());
    }
    /***
     * <p>Title: toEntity</p>  
     * <p>Description:  take json Convert string to object </p>  
     * @param <T>
     * @param value
     * @param clazz
     * @return
     */
    public static <T> T toEntity(String value, Class<T> clazz) {
    	return JSONObject.parseObject(value, clazz);
    }
    /***
     * <p>Title: toJSONStringIgnoreNullValue</p>  
     * <p>Description:  Convert object to json strand , The property value is null It doesn't show up </p>  
     * @param <T>
     * @param object
     * @return
     */
    public static <T> String toJSONStringIgnoreNullValue(T object) {
    	String result = JSONObject.toJSONString(object);
		return result;
    }
    /***
     * <p>Title: toJSONStringContainNullValue</p>  
     * <p>Description:  Convert object to json strand , The property value is null It will also show </p>  
     * @param <T>
     * @param object
     * @return
     */
    public static <T> String toJSONStringContainNullValue(T object) {
    	String result = JSONObject.toJSONString(object, SerializerFeature.WriteMapNullValue);
    	return result;
    }
    /***
     * <p>Title: toJSONStringValueFilter</p>  
     * <p>Description:  Convert object to json strand , Rewrite the value filter to handle the serialized values uniformly according to the rules </p>  
     * @param <T>
     * @param object
     * @return
     */
    public static <T> String toJSONStringValueFilter(T object) {
    	String result = JSONObject.toJSONString(object, new SimpleValueFilter());
    	return result;
    }