如何在 Java 中使用 @JsonSerialize 注释实现自定义序列化器?
javajsonobject oriented programmingprogramming
@JsonSerialize 注释用于在字段序列化期间声明自定义序列化器。我们可以通过扩展 StdSeralizer 类来实现自定义序列化器。并且需要重写 StdSerializer 类的 serialize() 方法。
语法
@Target(value={ANNOTATION_TYPE,METHOD,FIELD,TYPE,PARAMETER})
@Retention(value=RUNTIME)
public @interface JsonSerialize
In the below program, we can implement a custom serializer using @JsonSerialize annotation
示例
import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.*;
import com.fasterxml.jackson.databind.ser.std.*;
public class JsonSerializeAnnotationTest {
public static void main (String[] args) throws JsonProcessingException, IOException {
Employee emp = new Employee(115, "Adithya", new String[] {"Java", "Python", "Scala"});
ObjectMapper mapper = new ObjectMapper();
String jsonString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(emp);
System.out.println(jsonString);
}
}
// CustomSerializer class
class CustomSerializer extends StdSerializer {
public CustomSerializer(Class t) {
super(t);
}
public CustomSerializer() {
this(Employee.class);
}
@Override
public void serialize(Employee emp, JsonGenerator jgen, SerializerProvider sp) throws IOException, JsonGenerationException {
StringBuilder sb = new StringBuilder();
jgen.writeStartObject();
jgen.writeNumberField("id", emp.getId());
jgen.writeStringField("name", emp.getName());
for(String s: emp.getLanguages()) {
sb.append(s).append(";");
}
jgen.writeStringField("languages", sb.toString());
jgen.writeEndObject();
}
}
// Employee class
@JsonSerialize(using=CustomSerializer.class)class Employee {
private int id;
private String name;
private String[] languages;
public Employee(int id, String name, String[] languages) {
this.id = id;
this.name = name;
this.languages = languages;
}
public int getId() {
return this.id;
}
public String getName() {
return this.name;
}
public String[] getLanguages() {
return this.languages;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder("ID: ").append(this.id).append("\nName: ").append(this.name).append("\nLanguages:");
for(String s: this.languages) {
sb.append(" ").append(s);
}
return sb.toString();
}
}
输出
{
"id" : 115,
"name" : "Adithya",
"languages" : "Java;Python;Scala;"
}
