在Android中解释服务器数据

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前言

在这一篇文章中,主要讲一下如何使用Gson解释服务器返回的具有固定格式的数据。

分析

服务器:在本地使用nodejs的express框架建立的简单服务器。它返回了的数据如下:

var testArrayStr = "{\"data\": [{\"cnName\": \"jakewharton\",\"age\": 13,\"IsBoy\": true}, {\"cnName\": \"小红\",\"age\": 24,\"IsBoy\": false}],\"msg\": \"\",\"status\": 200}";

var testObjStr = "{\"data\": {\"cnName\": \"小红\",\"age\": 24,\"IsBoy\": false},\"msg\": \"\",\"status\": 200}";

res.end(testObjStr);

我们可以和服务器约定返回的格式模版如下,他们的主要区别是data,可以是对象或者对象的数组形式。

定义解释data为对象的模板:

public class BaseObjectResult<T> {
    public T data;
    public String msg;
    public int status;
}

定义解释data为数组的模版:

public class BaseArrayResult<T> {
    public List<T> data;
    public String msg;
    public int status;
}

实体对象: TestData.java

public class TestData {
    public String cnName;
    public int age;
    public boolean IsBoy;

    @Override
    public String toString() {
        return "testData:" +
                "cnName=" + this.cnName + " " +
                "age=" + this.age + " " +
                "IsBogy=" + this.IsBoy;
    }
}

使用retrofit和gson解释

自定义Converter.Factory

public class DecodeConverterFactory extends Converter.Factory {

    public static DecodeConverterFactory create() {
        return create(new Gson());
    }

    public static DecodeConverterFactory create(Gson gson) {
        return new DecodeConverterFactory(gson);
    }

    private final Gson gson;

    private DecodeConverterFactory(Gson gson) {
        if (gson == null) throw new NullPointerException("gson == null");
        this.gson = gson;
    }

    @Override
    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
        TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));
        return new CustomResponseBodyConverter<>(adapter, type);
    }

    @Override
    public Converter<?, RequestBody> requestBodyConverter(Type type, Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
        TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));
        return new DecodeRequestBodyConverter<>(gson, adapter);
    }

}

CustomResponseBodyConverter.java

public class CustomResponseBodyConverter<T> implements Converter<ResponseBody, T> {
    private final TypeAdapter<T> adapter;
    private Type mType;

    public CustomResponseBodyConverter(TypeAdapter<T> adapter, Type type) {
        this.adapter = adapter;
        this.mType = type;
    }

    @Override
    public T convert(ResponseBody value) throws IOException {
        //解密字符串
        if(mType == String.class) {
            return (T) value.string();
        } else {
            
        }
    }
}

DecodeRequestBodyConverter.java

public class DecodeRequestBodyConverter<T> implements Converter<T, RequestBody> {

    private static final MediaType MEDIA_TYPE = MediaType.parse("application/json; charset=UTF-8");
    private static final Charset UTF_8 = Charset.forName("UTF-8");

    private final Gson gson;
    private final TypeAdapter<T> adapter;
    DecodeRequestBodyConverter(Gson gson,TypeAdapter<T> adapter){
        this.gson = gson;
        this.adapter = adapter;
    }
    @Override
    public RequestBody convert(T value) throws IOException {
        Buffer buffer = new Buffer(); //value.toString()
        Writer writer = new OutputStreamWriter(buffer.outputStream(),UTF_8);
        JsonWriter jsonWriter = gson.newJsonWriter(writer);
        adapter.write(jsonWriter,value);
        jsonWriter.flush();
        return RequestBody.create(MEDIA_TYPE,buffer.readByteString());
    }

}

开始使用:

TestDataApi.java

public interface TestDataApi {
    @GET("/")
    Call<BaseObjectResult<TestData>> getArrayData();
}
当data为对象时:
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://192.168.20.168:3000")
                .addConverterFactory(DecodeConverterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        TestDataApi testDataApi = retrofit.create(TestDataApi.class);
        Call<BaseObjectResult<TestData>> resultCall = testDataApi.getArrayData();
        resultCall.enqueue(new Callback<BaseObjectResult<TestData>>() {
            @Override
            public void onResponse(Call<BaseObjectResult<TestData>> call, Response<BaseObjectResult<TestData>> response) {
                if(response.isSuccessful()) {
                    if(response.body() != null) {
                        TestData testData = response.body().data;
                        Log.d("hyj", "msg=" +  response.body().msg + "  "
                                + "status=" + response.body().status + "  "
                                + testData.toString());
                    }
                }

            }

            @Override
            public void onFailure(Call<BaseObjectResult<TestData>> call, Throwable t) {
                ToastUtil.showShort(mContext, t.getMessage());
            }
        });

输出的结果是:

04-08 16:04:56.053 31894-31894/com.zhangsunyucong.chanxa.testproject D/hyj: msg= status=200 testData:cnName=小红 age=24 IsBogy=false

当data为数组时:
Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://192.168.20.168:3000")
                .addConverterFactory(DecodeConverterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        TestDataApi testDataApi = retrofit.create(TestDataApi.class);
        Call<BaseArrayResult<TestData>> resultCall = testDataApi.getArrayData();
        resultCall.enqueue(new Callback<BaseArrayResult<TestData>>() {
            @Override
            public void onResponse(Call<BaseArrayResult<TestData>> call, Response<BaseArrayResult<TestData>> response) {
                if(response.isSuccessful()) {
                    if(response.body() != null) {
                        List<TestData> testData = response.body().data;
                        if(testData != null) {
                            for(int i = 0; i < testData.size(); i++) {
                                Log.d("hyj", "msg=" +  response.body().msg + "  "
                                        + "status=" + response.body().status + "  "
                                        + testData.get(i).toString());
                            }
                        }
                    }
                }
            }

            @Override
            public void onFailure(Call<BaseArrayResult<TestData>> call, Throwable t) {
                ToastUtil.showShort(mContext, t.getMessage());
            }
        });

输出的结果是:

04-08 16:11:44.703 32440-32440/com.zhangsunyucong.chanxa.testproject D/hyj: msg= status=200 testData:cnName=jakewharton age=13 IsBogy=true 04-08 16:11:44.703 32440-32440/com.zhangsunyucong.chanxa.testproject D/hyj: msg= status=200 testData:cnName=小红 age=24 IsBogy=false

手动解释####

关键的代码是:

    private ParameterizedType type(final Class raw, final Type... args) {
        return new ParameterizedType() {
            public Type getRawType() {
                return raw;
            }

            public Type[] getActualTypeArguments() {
                return args;
            }

            public Type getOwnerType() {
                return null;
            }
        };
    }

当data返回的是对象时:

TestDataApi testDataApi = retrofit.create(TestDataApi.class);
        Call<String> resultCall = testDataApi.getArrayData();
        resultCall.enqueue(new Callback<String>() {
            @Override
            public void onResponse(Call<String> call, Response<String> response) {
                if(response.isSuccessful()) {
                    if(response.body() != null) {
                        String testDataStr = response.body();
                        Gson gson = new Gson();

                        BaseObjectResult<TestData> testData = gson.fromJson(testDataStr,
                                type(BaseObjectResult.class, TestData.class));

                        Log.d("hyj", "msg=" +  testData.msg + "  "
                                + "status=" + testData.status + "  "
                                + testData.data.toString());
                    }
                }
            }

            @Override
            public void onFailure(Call<String> call, Throwable t) {
                ToastUtil.showShort(mContext, t.getMessage());
            }
        });

当返回的data是数组时:

TestDataApi testDataApi = retrofit.create(TestDataApi.class);
        Call<String> resultCall = testDataApi.getArrayData();
        resultCall.enqueue(new Callback<String>() {
            @Override
            public void onResponse(Call<String> call, Response<String> response) {
                if(response.isSuccessful()) {
                    if(response.body() != null) {
                        String testDataStr = response.body();
                        Gson gson = new Gson();

                        BaseArrayResult<TestData> testData = gson.fromJson(testDataStr,
                                type(BaseArrayResult.class, TestData.class));

                        if(testData != null && testData.data != null) {
                            for(int i = 0; i < testData.data.size(); i++) {
                                Log.d("hyj", "msg=" +  testData.msg + "  "
                                        + "status=" + testData.status + "  "
                                        + testData.data.get(i).toString());
                            }
                        }
                    }
                }
            }

            @Override
            public void onFailure(Call<String> call, Throwable t) {
                ToastUtil.showShort(mContext, t.getMessage());
            }
        });

它们返回的结果和第一种方法的返回结果是一样的。