如何在Java中使用@JsonSerialize注释实现自定义序列化程序?
该@JsonSerialize注释使用字段的序列化期间,宣布自定义序列。我们可以通过扩展StdSeralizer类来实现自定义序列化程序。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
在下面的程序中,我们可以使用@JsonSerialize注释实现自定义序列化程序
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类 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(); } } //员工阶层 @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(); } }
输出结果
{ "id" : 115, "name" : "Adithya", "languages" : "Java;Python;Scala;" }