java - 如何使用 Jackson 将嵌套的 ObjectId 序列化为 String？

Question

有many questions关于从 ObjectId 的转换至 String与 jackson 。所有答案都建议创建自己的 JsonSerializer<ObjectId>或注释 ObjectId字段 @JsonSerialize(using = ToStringSerializer.class) .

但是，我有一张 map 有时包含ObjectIds ，即:

class Whatever {
  private Map<String, Object> parameters = new HashMap<>();
  Whatever() {
    parameters.put("tom", "Cat");
    parameters.put("jerry", new ObjectId());
  }
}

我希望 jackson 将其转换为:

{
  "parameters": {
    "tom": "cat",
    "jerry": "57076a6ed1c5d61930a238c5"
  }
}

但是我得到:

{
  "parameters": {
    "tom": "cat",
    "jerry": {
      "date": 1460103790000,
      "machineIdentifier": 13747670,
      "processIdentifier": 6448,
      "counter": 10631365,
      "time": 1460103790000,
      "timestamp": 1460103790,
      "timeSecond": 1460103790
    }
  }
}

我已经用

注册了转换(在 Spring 中)

public class WebappConfig extends WebMvcConfigurerAdapter {
  @Override
  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    builder
        .serializerByType(ObjectId.class, new ToStringSerializer());
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter(builder.build());
    converters.add(converter);
  }
}

和一级ObjectIds被正确转换。如何让 jackson 也转换嵌套的？我是否必须为此 map 编写自定义转换器？

请记住，这 Map可以嵌套多次(即包含另一个 map )。我只想转换 ObjectId至 String每当 jackson 看到它。

Answer 1

我想您正在从 org.springframework.boot:spring-boot-starter-data-mongodb 获取 org.bson.types.ObjectId。你的代码对我来说工作得很好。我能看到的一件事是您没有在 WebappConfig 上方显示 @Configuration 注释。

这是我的演示项目，你能在你的设置上测试一下吗？

应用程序.java

import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import org.bson.types.ObjectId;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

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

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Configuration
    public static class WebappConfig extends WebMvcConfigurerAdapter {
        @Override
        public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
            Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
            builder
                    .serializerByType(ObjectId.class, new ToStringSerializer());
            MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter(builder.build());
            converters.add(converter);
        }
    }

    @RestController
    public static class MyRestController {

        @ResponseBody
        @RequestMapping("/")
        public Whatever method() {
            return new Whatever();
        }
    }

    public static class Whatever {
        private Map<String, Object> parameters = new HashMap<>();

        public Whatever() {
            parameters.put("tom", "Cat");
            parameters.put("jerry", new ObjectId());
        }

        public Map<String, Object> getParameters() {
            return parameters;
        }

        public void setParameters(Map<String, Object> parameters) {
            this.parameters = parameters;
        }
    }
}

来自 127.0.0.1:8080 的响应

{
  "parameters": {
    "tom": "Cat",
    "jerry": "5709df1cf0d9550b4de619d2"
  }
}

Gradle :

dependencies {
    compile("org.springframework.boot:spring-boot-starter-data-mongodb")
    compile("org.springframework.boot:spring-boot-starter-web")
}