如何使用Java中的排除過濾器將一個bean轉換為JSON物件？

可以使用JsonConfig類別來配置序列化過程。我們可以使用JsonConfig的setJsonPropertyFilter()方法來設定在序列化為JSON時的屬性篩選器。我們需要透過重寫PropertyFilter介面的apply()方法來實作一個自訂的PropertyFilter類別。如果屬性將被過濾掉，則傳回true，否則傳回false。

語法

public void setJsonPropertyFilter(PropertyFilter jsonPropertyFilter)

Example

import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.util.PropertyFilter;
public class ConvertBeanToJsonExcludeFilterTest {
   public static void main(String[] args) {
      Student student = new Student("Sai", "Chaitanya", 20, "Hyderabad");
      JsonConfig jsonConfig = new JsonConfig();
      jsonConfig.setJsonPropertyFilter(new CustomPropertyFilter());

      JSONObject jsonObj = JSONObject.fromObject(student, jsonConfig);
      System.out.println(jsonObj.toString(3)); //pretty print JSON
   }
   public static class Student {
      private String firstName, lastName, address;
      public int age;
      public Student(String firstName, String lastName, int age, String address) {
         super();
         this.firstName = firstName;
         this.lastName = lastName;
         this.age = age;
         this.address = address;
      }
      public String getFirstName() {
         return firstName;
      }
      public String getLastName() {
         return lastName;
      }
      public int getAge() {
         return age;
      }
      public String getAddress() {
         return address;
      }
   }
}
// CustomPropertyFilter class
class CustomPropertyFilter implements PropertyFilter {
   @Override
   public boolean apply(Object source, String name, Object value) {
      if(Number.class.isAssignableFrom(value.getClass()) ||        String.class.isAssignableFrom(value.getClass())) {
         return false;
      }
      return true;
   }
}

輸出

{
  "firstName": "Sai",
  "lastName": "Chaitanya",
  "address": "Hyderabad",
  "age": 20
}

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