MessageBodyReader 是否支持 DTO 类？

Question

我想使用Grails-jaxrs plugin 来实现自定义MessageBodyReaderSupport 以从客户端读取UserDto 类。

我必须如何实现 UserDtoReader 才能获取 UserDto 的实例？

这是我的 UserDto 类：

public class UserDto {
    private String firstName;
    private String lastName;

    public UserDto() {
        firstName = "";
        lastName = "";
    }

    public UserDto(String firstName,
                   String lastName) {

        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }


    @Override
    public String toString() {
        String s = " { User ";
        s += "id=" + id + " ";
        s += "firstName=" + firstName + " ";
        s += "lastName=" + lastName + " ";
        s += " User } ";
        return s;
    }
}

这是我的 UserDtoReader 类：

@Consumes("application/json")
class UserDtoReader extends MessageBodyReaderSupport<UserDto> {

    @Override
    public UserDto readFrom(MultivaluedMap<String, String> httpHeaders,
            InputStream entityStream) throws IOException,
            WebApplicationException {
        // TODO Auto-generated method stub
        return null;
    }
}

Answer 1

使用这个：

@Consumes("application/json")
class UserDtoReader extends MessageBodyReaderSupport<UserDto> {

    @Override
    public UserDto readFrom(MultivaluedMap<String, String> httpHeaders,
            InputStream entityStream) throws IOException,
            WebApplicationException {
        return new JsonSlurper().parse(new InputStreamReader(entityStream))
    }
}

Answer 2

@Provider
@Consumes(MediaType.APPLICATION_JSON)
public final class UserDtoReader implements MessageBodyReader<UserDto> {

    private static final String UTF_8 = "UTF-8";
    private Gson gson;

    private Gson getGson() {
        if (gson == null) {
            final GsonBuilder gsonBuilder = new GsonBuilder();
            gson = gsonBuilder.create();
        }
        return gson;
    }

    public UserDto readFrom(java.lang.Class<UserDto> type,
            java.lang.reflect.Type genericType,
            java.lang.annotation.Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<java.lang.String, java.lang.String> httpHeaders,
            java.io.InputStream entityStream) throws IOException {
        InputStreamReader streamReader = new InputStreamReader(entityStream,UTF_8);

        try {
            Type jsonType;
            if (type.equals(genericType)) 
             jsonType = type;
            else 
             jsonType = genericType;

                     UserDto userDto = getGson().fromJson(streamReader, jsonType);
            return userDto;
        } finally { streamReader.close();}
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType,
            java.lang.annotation.Annotation[] annotations, MediaType mediaType) {
        return true;
    }

}

你可以从here下载谷歌Gson

配置

JAX-RS 资源类和提供程序类的子集（MessageBodyReaders 和 MessageBodyWriters）。这些类通过 javax.ws.rs.core.Application 类的扩展在 JAX-RS 运行时中配置。

public class ApplicationConfig extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        Set<Class<?>> resources = new java.util.HashSet<>();
        resources.add(UserDtoReader.class);
        return resources;
    }