將子類序列化爲子元素

Question

我正在使用Jackson並希望將子類的字段序列化爲子元素。不幸的是，傑克遜的文件很糟糕

@JsonRootName(value = "subclass") 
public class ProfilerTask extends Task { 

    private int age; 

    private int grade; 



    public ProfilerTask(String name, Date createdOn, int age, int grade) { 
     super(name, createdOn); 
     this.age = age; 
     this.grade = grade; 
    } 

    /** 
    * @return the age 
    */ 
    public int getAge() { 
     return age; 
    } 

    /** 
    * @return the grade 
    */ 
    public int getGrade() { 
     return grade; 
    } 

} 

我得到這個：{"name":"test task","createdOn":1372771395040,"age":25,"grade":4}，而其實我是想子類的字段是一個子元素。

Answer 1

我想，你應該考慮構圖而不是繼承。但是如果你真的想繼承，你必須改變POJO類。您可以創建新的內部類並將所有屬性和字段移動到這個新類中。見我的例子：

public class ProfilerTask extends Task { 

    private Subclass subclass; 

    public ProfilerTask(String name, long createdOn, int age, int grade) { 
     super(name, createdOn); 
     this.subclass = new Subclass(); 
     this.subclass.age = age; 
     this.subclass.grade = grade; 
    } 

    public Subclass getSubclass() { 
     return subclass; 
    } 

    @JsonIgnore 
    public int getAge() { 
     return subclass.age; 
    } 

    @JsonIgnore 
    public int getGrade() { 
     return subclass.grade; 
    } 

    public class Subclass { 
     private int age; 
     private int grade; 

     public int getAge() { 
      return age; 
     } 

     public void setAge(int age) { 
      this.age = age; 
     } 

     public int getGrade() { 
      return grade; 
     } 

     public void setGrade(int grade) { 
      this.grade = grade; 
     } 
    } 
} 

現在，請看看我的簡單的main方法：

ObjectMapper mapper = new ObjectMapper(); 
ProfilerTask task = new ProfilerTask("test task", 1372771395040L, 25, 4); 

System.out.println(mapper.writeValueAsString(task)); 

這個程序打印：

{"name":"test task","createdOn":1372771395040,"subclass":{"age":25,"grade":4}} 

我覺得這是創建子元素的最簡單方法在與傑克遜的JSON中。