Jackson忽略为空的字段

1.概述

如何在序列化Java类时将Jackson设置为忽略空字段。

2.忽略类中的空字段

jackjson允许在任何一个类上控制这种行为：

@JsonInclude(Include.NON_NULL)
public class MyDto {
    
     ... }

或更详细地在字段级别：

@Data
public class MyDtoField {
    
    
    @JsonInclude(JsonInclude.Include.NON_NULL)
    private String stringValue;
    private int intValue;
}

@Test
    public void test22() throws JsonProcessingException {
    
    
        ObjectMapper mapper = new ObjectMapper();
        MyDtoField dtoObject = new MyDtoField();

        String dtoAsString = mapper.writeValueAsString(dtoObject);
        System.out.println(dtoAsString);//{"intValue":0}

        assertThat(dtoAsString, containsString("intValue"));
        assertThat(dtoAsString, not(containsString("stringValue")));
    }

3.全局忽略空字段

Jackson还允许我们在ObjectMapper上全局配置此行为：

mapper.setSerializationInclusion(Include.NON_NULL);

@Data
public class MyDtoGlobalField {
    
    
    private String stringValue;
    private int intValue;
    private boolean booleanValue;
}

 @Test
public void test23() throws JsonProcessingException {
    
    
    ObjectMapper mapper = new ObjectMapper();
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    MyDtoGlobalField dtoObject = new MyDtoGlobalField();

    String dtoAsString = mapper.writeValueAsString(dtoObject);
    System.out.println(dtoAsString);//{"intValue":0,"booleanValue":false}
    assertThat(dtoAsString, containsString("intValue"));
    assertThat(dtoAsString, containsString("booleanValue"));
    assertThat(dtoAsString, not(containsString("stringValue")));
}