永恒的龙目岛与杰克逊注释的类 [英] Immutable Lombok annotated class with Jackson

问题描述

创建类的首选方法是什么

• 不可变


• 可以序列化/用杰克逊反序列化


• 人类可读且模板水平较低

最好是，我会喜欢这样的东西：

  @Data（onConstructor = @__（@ JsonCreator））
  

然后将所有字段设为 private final 。但是，这甚至没有编译（我不知道为什么）。使用

  @AllArgsConstructor（onConstructor = @__（@ JsonCreator））
  

将编译但仅产生

  InvalidDefinitionException：未找到序列化程序for class 
  

解决方案

你可以使用龙目岛的

这是一个用于验证序列化/反序列化的JUnit测试：

  public class PointTest extends Assert {
 
 private ObjectMapper objectMapper = new ObjectMapper（）; 
 
 @Test 
 public void testSerialize（）throws IOException {
 Point point = new Point（10,20）; 
 String json = objectMapper.writeValueAsString（point）; 
 assertEquals（{\x \：10，\y \：20}，json）; 
} 
 
 @Test 
 public void testDeserialize（）throws IOException {
 String json ={\x \：10，\y \ ：20}; 
 Point point = objectMapper.readValue（json，Point.class）; 
 assertEquals（new Point（10,20），point）; 
} 
} 
  

What is the preferred way to create class that is

• Immutable
• Can be serialized/deserialized with Jackson
• Human-readable and with low level of boilerplate

Preferably, I would have liked something like this to work:

@Data(onConstructor = @__(@JsonCreator))

and then have all fields to be private final. However, this does not even compile (and I'm not sure why). Using

@AllArgsConstructor(onConstructor = @__(@JsonCreator))

will compile but only yields

InvalidDefinitionException: No serializer found for class

解决方案

You can use Lombok's @Builder annotation to generate a builder for your immutable POJO class. But making the Lombok-generated builder usable by Jackson's deserialization is somewhat tricky.

• You need to annotate your POJO class with @JsonDeserialize(builder = ...) to tell Jackson which is the builder class to use.
• You need to annotate the builder class with @JsonPOJOBuilder(withPrefix = "") to tell Jackson that its setter-methods do not start with with.

Example:

An immutable POJO class:

@Data
@Builder(builderClassName = "PointBuilder")
@JsonDeserialize(builder = Point.PointBuilder.class)
public class Point {

    private final int x;

    private final int y;

    @JsonPOJOBuilder(withPrefix = "")
    public static class PointBuilder {
        // Lombok will add constructor, setters, build method
    }
}

Here is a JUnit test to verify the serialization/deserialization:

public class PointTest extends Assert {

    private ObjectMapper objectMapper = new ObjectMapper();

    @Test
    public void testSerialize() throws IOException {
        Point point = new Point(10, 20);
        String json = objectMapper.writeValueAsString(point);
        assertEquals("{\"x\":10,\"y\":20}", json);
    }

    @Test
    public void testDeserialize() throws IOException {
        String json = "{\"x\":10,\"y\":20}";
        Point point = objectMapper.readValue(json, Point.class);
        assertEquals(new Point(10, 20), point);
    }
}

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