杰克逊忽略了外部库中超类的所有属性 [英] Jackson ignore all properties of superclass from external library

问题描述

我正在使用ORM进行开发，我扩展了一个基础orm类来创建表。

I am developing using an ORM where I extend a base orm class to create tables.

例如：

public class Person extends DbItem {
    @JsonIgnore
    private String index;

    private String firstName;

    private String lastName;
}

问题是，当我使用ObjectMapper进行序列化时，它会尝试序列化成员DbItem类。有没有简单的方法来防止这种情况？例如，有一个注释。

Problem is that when I use ObjectMapper to serialize, it tries to serialize the members of the DbItem class. Is there any simple way to prevent this? For example with an annotation.

我看了一个类似的问题杰克逊序列化：如何忽略超类属性但我希望它可以做得更简单，我不确定我是否可以这样做，因为我无法改变超类，因为它在外部库中。

I had a look at a similar problem Jackson serialization: how to ignore superclass properties but I was hoping it could be done simpler, and I'm not sure if I could do it as I can't change the superclass since it is in an external library.

推荐答案

您可以使用混合或 @JsonIgnoreProperties

出于此目的在这些示例中，基本ORM类和扩展名假定为：

You can use a Mix-in or @JsonIgnoreProperties

For the purposes of these examples, the base ORM class and extension are assumed to be:

public class DbItem {
    public String dbPropertyA;
    public String dbPropertyB;
}

和

public class Person extends DbItem {
    public String index;
    public String firstName;
    public String lastName;
}

。

混合是杰克逊从对象本身理解的de /序列化指令的抽象。这是一种自定义第三方类的de / serialization的方法。为了定义混合，必须使用 ObjectMapper 创建并注册抽象类。

A Mix-in is an abstraction of the de/serialization instructions that Jackson understands from an object itself. It is a way to customize de/serialization of 3rd party classes. In order to define a Mix-in, an abstract class must be created and registered with the ObjectMapper.

public abstract class PersonMixIn {
    @JsonIgnore public String dbPropertyA;
    @JsonIgnore public String dbPropertyB;
    @JsonIgnore public String index;
}

注册混合

Registering the Mix-in

@Test
public void serializePersonWithMixIn() throws JsonProcessingException {
    // set up test data including parent properties
    Person person = makeFakePerson();

    // register the mix in
    ObjectMapper om = new ObjectMapper()
            .addMixIn(Person.class, PersonMixIn.class);

    // translate object to JSON string using Jackson
    String json = om.writeValueAsString(person);

    assertFalse(json.contains("dbPropertyA"));
    assertFalse(json.contains("dbPropertyB"));
    assertFalse(json.contains("index"));
    System.out.println(json);
}

@JsonIgnoreProperties

如果你想避免创建一个类并配置 ObjectMapper ，那么 @JsonIgnoreProperties 可以使用注释。只需注释要序列化的类，并列出要排除的属性。

@JsonIgnoreProperties

If you want to avoid creating a class and configuring the ObjectMapper, the @JsonIgnoreProperties annotation can be utilized. Simply annotate the class you are serializing and list the properties to exclude.

@JsonIgnoreProperties({"index", "dbPropertyA", "dbPropertyB"})
public class Person extends DbItem {
    public String index;
    public String firstName;
    public String lastName;
}

See It In Action

See It In Action

@Test
public void serializePersonWithIgnorePropertiesAnnotation() throws JsonProcessingException {
    // set up test data including parent properties
    Person person = makeFakePerson();

    ObjectMapper om = new ObjectMapper();

    // translate object to JSON string using Jackson
    String json = om.writeValueAsString(person);

    assertFalse(json.contains("dbPropertyA"));
    assertFalse(json.contains("dbPropertyB"));
    assertFalse(json.contains("index"));
    System.out.println(json);
}

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