何时在 Java 中使用 Jackson 的 @JsonValue 注释?\
javajsonobject oriented programmingprogramming
@JsonValue 注释 在方法级别很有用。我们可以使用此注释从 Java 对象生成 JSON 字符串。如果我们想打印序列化对象，则覆盖 toString() 方法。但使用 @JsonValue 注释，我们可以定义一种序列化 Java 对象的方式。
语法
@Target(value={ANNOTATION_TYPE,METHOD,FIELD})
@Retention(value=RUNTIME)
public @interface JsonValue
示例
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonValue;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
public class JsonValueAnnotationTest {
public static void main(String args[]) throws Exception {
ObjectMapper mapper = new ObjectMapper();
String jsonString = mapper.writeValueAsString(new Student());
System.out.println(jsonString);
}
}
// Student class
class Student {
@JsonProperty
private int studentId = 115;
@JsonProperty
private String studentName = "Sai Adithya";
@JsonValue
public String toJson() {
return this.studentName + "," + this.studentId + "," + this.toString();
}
@Override
public String toString() {
return "Student[" +
"studentId = " + studentId +
", studentName = " + studentName +
']';
}
}
输出
"Sai Adithya,115,Student[studentId = 115, studentName = Sai Adithya]"
