Jackson mixin：如何将 class 中的字段忽略或重命名为树

Question

我正在尝试从表示为树的 class 进行深度过滤（重命名/忽略字段）。

使用 Jackson Mixin，我可以从根级别重命名或忽略字段。我想要实现的是如何在多个级别上进行过滤（重命名/忽略）？

例如，我有一棵有两个 class 的树。 Class A 是根，B 是树中的第二层深度。通过应用 Jackson Mxiin，我想从根 A 过滤属性 a2，从 B 过滤属性 b1。

Class 代表根的A class

public class A {
  private String a1;
  private String a2;
  private B b;

  public A(String a1, String a2, B b) {
      this.a1 = a1;
      this.a2 = a2;
      this.b = b;
  }

  public String getA1() {
      return a1;
  }

  public void setA1(String a1) {
      this.a1 = a1;
  }

  public String getA2() {
      return a2;
  }

  public void setA2(String a2) {
      this.a2 = a2;
  }

  public B getB() {
      return b;
  }

  public void setB(B b) {
      this.b = b;
  }

}

Class B - 二级深度

public class B {

      private String b1;
      private String b2;

      public B(String b2, String b1) {
          this.b1 = b1;
          this.b2 = b2;
      }

      public String getB1() {
          return b1;
      }

      public void setB1(String b1) {
          this.b1 = b1;
      }

      public String getB2() {
          return b2;
      }

      public void setB2(String b2) {
          this.b2 = b2;
      }
    }

过滤器

public interface AMixIn {
  // Filter for A (implemented to filter second depth as well)
  @JsonIgnore
  String getA2();

  @JsonIgnore
  public BMixIn getB();
}

public interface BMixIn {
  // Filter for B
  @JsonIgnore
  public String getB1();

}

测试

public class SecondLevelTest {
  // Test
  private ObjectMapper mapper = null;
  private ObjectWriter writer = null;

  @Before
  public void setUp() {
      // init
      mapper = new ObjectMapper();
      mapper.setMixIns(ImmutableMap.<Class<?>, Class<?>>of(A.class, AMixIn.class));
      writer = mapper.writer().with(SerializationFeature.INDENT_OUTPUT);
  }

  @Test
  public void rename_field_jackson() throws JsonProcessingException {

      B b = new B("vb1", "vb2");
      A a = new A("va1", "va2", b);

      // I want to get this result
      // {
      // "a1" : "va1",
      // "b2" : "vb2"
      // }
      String json = writer.writeValueAsString(a);
      System.out.println(json);
  }
}

Answer 1

这应该会为您提供所需的输出。将 setUp() 更改为也使用 BMixIn:

@Before
public void setUp() {
    // init
    mapper = new ObjectMapper();
    mapper.setMixIns(ImmutableMap.of(A.class, AMixIn.class, B.class, BMixIn.class));
    writer = mapper.writer().with(SerializationFeature.INDENT_OUTPUT);
}

并更改 AMixIn 以展开 B

public interface AMixIn {
    // Filter for A (implemented to filter second depth as well)
    @JsonIgnore
    String getA2();

    @JsonUnwrapped
    public BMixIn getB();
}

忘记注册 BMixIn 导致其 @JsonIgnore 永远无法使用。 @JsonUnwrapped 取消嵌套 b 所以你得到一个平面结构。

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