java - 如何使用 Jackson 序列化声明性链接( Jersey )

Question

我在我的项目中使用声明性链接。我的 jackson 映射器配置是

final ObjectMapper mapper = new ObjectMapper();
    mapper.configure(MapperFeature.DEFAULT_VIEW_INCLUSION, false);
    mapper.configure(MapperFeature.AUTO_DETECT_FIELDS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_IS_GETTERS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_GETTERS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_SETTERS, false);
    mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    mapper.configure(SerializationFeature.INDENT_OUTPUT, true);

由于我禁用了任何类型的自动检测，注入(inject)的链接如

    @InjectLinks({

@InjectLink(rel = "bookmark", resource = ConnectionsResource.class, style = Style.ABSOLUTE_PATH) })
@JsonProperty("links")
Link[] links;

被序列化为空的 JSON 对象(因为“Link”中的任何字段都没有使用 @JsonProperty 进行注释)。

如何在不更改全局映射器配置的情况下仅对字段 rel 和 href 启用链接序列化？

Answer 1

因此，实现此目的的一种方法是使用客户序列化程序。您必须为此序列化程序添加一个新模块到ObjectMapper，但这不应影响其余配置。

这是序列化器

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import java.io.IOException;
import javax.ws.rs.core.Link;

public class LinkSerializer extends JsonSerializer<Link>{

    @Override
    public void serialize(Link link, JsonGenerator jg, SerializerProvider sp) 
            throws IOException, JsonProcessingException {
        jg.writeStartObject();
        jg.writeStringField("rel", link.getRel());
        jg.writeStringField("href", link.getUri().toString());
        jg.writeEndObject();
    }
}

这里是一个测试类

public class TestClass {

    @JsonProperty("links")
    protected List<Link> links;
    protected String name;
    protected String id;
    // getter and setters
}

以及测试运行

public static void main(String[] args) throws Exception{

    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(MapperFeature.DEFAULT_VIEW_INCLUSION, false);
    mapper.configure(MapperFeature.AUTO_DETECT_FIELDS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_IS_GETTERS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_GETTERS, false);
    mapper.configure(MapperFeature.AUTO_DETECT_SETTERS, false);
    mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    mapper.configure(SerializationFeature.INDENT_OUTPUT, true);

    SimpleModule simpleModule = new SimpleModule();
    simpleModule.addSerializer(Link.class, new LinkSerializer());
    mapper.registerModule(simpleModule);

    Link link1 = Link.fromUri(URI.create("http://localhost:8080/")).rel("one").build();
    Link link2 = Link.fromUri(URI.create("http://localhost:8080/")).rel("two").build();
    TestClass test = new TestClass();
    test.getLinks().add(link1);
    test.getLinks().add(link2);
    String json = mapper.writeValueAsString(test);
    System.out.println(json);
}

产生这个结果

{
  "links" : [ {
    "rel" : "one",
    "href" : "http://localhost:8080/"
  }, {
    "rel" : "two",
    "href" : "http://localhost:8080/"
  } ]
}

希望这有帮助。