Question

我试图让杰克逊忽略DTO的一些属性，但我似乎无法做到。我有一个相当大的项目，有很多依赖项（Lombok，Spring，GWT，Gemfire等等），我无法改变这些依赖关系（也许我可以更改版本，但它不是我的电话）。

我准备了一个测试用例，这里是：

这是我的测试dto类，它有一个只有用的地图服务器端。该dto的副本被序列化以发送给gwt 显示（执行不完整，只有相关部分显示）。

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreType;
import lombok.*;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode(of = "id", callSuper = true)
public class MyClass extends MyAbstractClass {

    @Getter
    @Setter
    @Builder
    public static class AValueClass {
        int someInt;
        String SomeString;
    }

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    @JsonIgnoreType
    public static class MyJsonIgnoreKeyClass {
        protected Integer anInt;
        protected String aString;
    }

    @JsonIgnore
    @Getter(AccessLevel.NONE) @Setter(AccessLevel.NONE)
    private transient Map<MyJsonIgnoreKeyClass, List<AValueClass>> aMapThatJacksonShouldIgnore = new HashMap<>();


    public void addToMap(MyJsonIgnoreKeyClass key, AValueClass value) {
        List<AValueClass> valueList = aMapThatJacksonShouldIgnore.get(key);
        if(valueList == null) {
           valueList = new ArrayList<>();
        }
        valueList.add(value);
        aMapThatJacksonShouldIgnore.put(key,valueList);
    }

    public boolean noMap() {
        return aMapThatJacksonShouldIgnore == null || aMapThatJacksonShouldIgnore.keySet().isEmpty();
    }

    public void nullifyMap() {
        aMapThatJacksonShouldIgnore = null;
    }

    // other methods operating on maps omitted
}

测试模型继承了超类

中的一些字段

import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;

import java.util.Date;

@Setter
@Getter
@EqualsAndHashCode(of = "id")
public class MyAbstractClass {

    protected String id;
    protected Date aDay;
}

这是我准备的单元测试

public class MyClassJacksonTest {

    ObjectMapper om;

    @Before
    public void setUp() throws Exception {
        om = new ObjectMapper().registerModule(new Jdk8Module());
        om.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        om.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    }

    @Test
    public void testWithMapValues() throws Exception {
        MyClass testClass = new MyClass();
        testClass.setADay(new Date());
        testClass.setId(UUID.randomUUID().toString());
        testClass.addToMap(
                new MyClass.MyJsonIgnoreKeyClass(1,"test"),
                new MyClass.AValueClass(1,"test"));

        StringWriter writer = new StringWriter();
        om.writeValue(writer,testClass);
        writer.flush();
        String there = writer.toString();
        MyClass andBackAgain = om.readValue(there, MyClass.class);

        assertTrue(andBackAgain.noMap());
    }

    @Test
    public void testWithEmptyMaps() throws Exception {
        MyClass testClass = new MyClass();
        testClass.setADay(new Date());
        testClass.setId(UUID.randomUUID().toString());

        StringWriter writer = new StringWriter();
        om.writeValue(writer,testClass);
        writer.flush();
        String there = writer.toString();
        MyClass andBackAgain = om.readValue(there, MyClass.class);

        assertTrue(andBackAgain.noMap());
    }

    @Test
    public void testWithNullMaps() throws Exception {
        MyClass testClass = new MyClass();
        testClass.setADay(new Date());
        testClass.setId(UUID.randomUUID().toString());
        testClass.nullifyMap();

        StringWriter writer = new StringWriter();
        om.writeValue(writer,testClass);
        writer.flush();
        String there = writer.toString();
        MyClass andBackAgain = om.readValue(there, MyClass.class);

        assertTrue(andBackAgain.noMap());
    }

}

所有测试都失败了

com.fasterxml.jackson.databind.JsonMappingException: Can not find a (Map) Key deserializer for type [simple type, class MyClass$MyJsonIgnoreKeyClass]

所以问题是：为什么杰克逊试图为无法访问的地图的密钥找到解串器（因为没有getter和setter）并且用@JsonIgnore进行注释？更重要的是，我怎么能告诉它不要搜索反序列化器？

这些是我的pom上的相关依赖项，如果它可以提供任何帮助：

<properties>
    <!-- ... -->
    <jackson.version>2.7.4</jackson.version>
</properties>

<dependencies>
  <!-- other dependencies omitted -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.module</groupId>
        <artifactId>jackson-module-jsonSchema</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-jdk8</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-jsr353</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-xml</artifactId>
        <version>${jackson.version}</version>
        <exclusions>
            <exclusion>
                <groupId>org.codehaus.woodstox</groupId>
                <artifactId>stax2-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

Answer 1

事实证明，这是龙目岛与杰克逊之间不良互动的情况。 Lombok注释@AllArgsConstructor生成一个使用@ConstructorProperties注释的构造函数，该构造函数依次列出在类中声明的所有属性。然后，当使用默认的解串器时，Jackson会使用它。在这种情况下，不考虑不存在setter和getter以及是否存在@JsonIgnore注释。

解决方案只是指定属性@AllArgsConstructor设置为true的suppressConstructorProperties：

@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor(suppressConstructorProperties = true)
@EqualsAndHashCode(of = "id", callSuper = true)
public class MyClass extends MyAbstractClass {
  // everything else is unchanged

Answer 2

确实很棘手。我认为正在发生的是你正在使用Lombok生成一个公共的所有参数构造函数。反序列化时，杰克逊将试图使用它。如果您将MyClass的注释更改为

@AllArgsConstructor(access = AccessLevel.PRIVATE)

......它应该可以正常工作。祝你好运！

杰克逊忽略了@Ignore注释

2 个答案: