Retrofit 和 Jackson 以及解析 JSON

Question

我正在使用 Jackson 的 Retrofit。由于某些原因，我无法解析以下 JSON：

[
    {
        "ProfileImage": null,
        "UserName": "joe"
    },
    {
        "ProfileImage": "http://www.example.com/profiles/fileName1.jpg",
        "UserName": "jane"
    },
    {
        "ProfileImage": null,
        "UserName": "john"
    }
]

我得到了这个例外：

Exception in thread "main" retrofit.RetrofitError: java.lang.ClassCastException: 
    sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl 
    cannot be cast to java.lang.Class

at retrofit.RetrofitError.unexpectedError(RetrofitError.java:41)
at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:294)
at retrofit.RestAdapter$RestHandler.invoke(RestAdapter.java:182)
at com.sun.proxy.$Proxy5.getReplies(Unknown Source)
at Test.main(Test.java:25)

Caused by: java.lang.ClassCastException: 
    sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl 
    cannot be cast to java.lang.Class

at JacksonConverter.fromBody(JacksonConverter.java:27)
at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:274)

我的代码如下：

//文件：Test.java:

public class Test { 
    public static void main(String[] args) {

        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(new PropertyNamingStrategy
                                                 .PascalCaseStrategy());

        RestAdapter restAdapter = new RestAdapter.Builder()
                                      .setServer("http://www.example.com")
                                      .setConverter(new JacksonConverter(mapper))
                                      .build();

        ListingService listingService = restAdapter.create(ListingService.class);
        ArrayList<ListingReplyExt> replies = listingService.getReplies(123, 1, 10);
        //More code...
}

}

//文件：ListingService.java

public interface ListingService {       
    @GET("/api/ListingRepliesService.svc/Get")
    public ArrayList<ListingReplyExt> getReplies(
                                           @Query("listingId") long listingId,
                                           @Query("start") int start,
                                           @Query("count") int count);
}

//文件：ListingReplyExt.java:

@JsonIgnoreProperties(ignoreUnknown = true)
public class ListingReplyExt {

    private String profileImage;
    private String username;

    @JsonProperty(value = "ProfileImage")
    public String getProfileImage() {
        return profileImage;
    }

    @JsonProperty(value = "ProfileImage")
    public void setProfileImage(String profileImage) {
        this.profileImage = profileImage;
    }

    @JsonProperty(value = "UserName")
    public String getUsername() {
        return username;
    }

    @JsonProperty(value = "UserName")
    public void setUsername(String username) {
        this.username = username;
    }
}

如有任何帮助，我们将不胜感激。

更新

Sotirios Delimanolis 的评论给了我一些解决这个问题的提示。

我的 JacksonConverter 原来是这样的：

public class JacksonConverter implements Converter {
    private final ObjectMapper objectMapper;

    public JacksonConverter(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override public Object fromBody(TypedInput body, Type type) {
        return objectMapper.readValue(body.in(), (Class<Object>) type);
    }

    //More code
}

我把它改成这样：

public class JacksonConverter implements Converter {
    private final ObjectMapper objectMapper;

    public JacksonConverter(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override public Object fromBody(TypedInput body, Type type) {
        JavaType javaType = objectMapper.getTypeFactory().constructType(type);
        return objectMapper.readValue(body.in(), javaType);
    }

    //More code
}

现在它对我有用。

Answer 1

通过将其添加到您的 build.gradle 来使用 Square 的转换器：

compile 'com.squareup.retrofit:converter-jackson:1.9.0'

之后，您可以通过将

.setConverter(new JacksonConverter())

添加到您的

RestAdapter

构建器来激活它。

Answer 2

在新版本的 OkHttp 中，似乎已经完成了：

Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(API_URL)
                .addConverterFactory(JacksonConverterFactory.create())
                .build();