OkHttp的使用与跳坑示例

mark

OkHttp是一个优秀的网络请求框架,我开始接触Android开发的时候就用过这个网络请求框架,官方的参考文档在这里 https://square.github.io/okhttp/ ,本文演示了使用OkHttp框架进行简单的Get、Post(表单形式和JSON形式)、Delete、附加请求头、请求异步回调,文件的上传和下载等常用操作。最后记录了一个今天调试了很久的坑,那就是response.body().string()只能有效调用一次,注意Debug的时候对结果造成的改变!JDK9的HttpURLConnection有很多变化,下次博客中会有演示和说明。

首选引入这个依赖就可以使用OkHTTP了

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<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>3.6.0</version>
</dependency>

<!-- 这个是我演示Post请求JSON格式的时候用到的 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>

如果是 gradle 管理的项目,则只需要引入:

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compile 'com.squareup.okhttp3:okhttp:3.6.0'

1、Get请求示例

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String url = "http://zouchanglin.cn";
OkHttpClient okHttpClient = new OkHttpClient();
Request request = new Request.Builder().get().url(url).build();
try {
Response execute = okHttpClient.newCall(request).execute();
System.out.println(execute.body().string());
} catch (IOException e) {
e.printStackTrace();
}

2、Post请求示例

1、JSON请求

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public static void main(String[] args) {
String url = "http://zouchanglin.cn/info/create";
OkHttpClient okHttpClient = new OkHttpClient();
Map<String, Object> map = new HashMap<>();
map.put("name", "Mike");
map.put("age", "20");
RequestBody requestBody = RequestBody.create(
MediaType.parse("application/json; charset=utf-8"),
JSONObject.toJSONString(map));
Request request = new Request.Builder().post(requestBody).url(url).build();
try {
Response response = okHttpClient.newCall(request).execute();
System.out.println(response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}

2、表单数据

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public static void main(String[] args) {
String url = "http://zouchanglin.cn/info/create";
OkHttpClient okHttpClient = new OkHttpClient();
RequestBody requestBody = new FormBody.Builder()
.add("name", "Mike")
.add("age", "20").build();
Request request = new Request.Builder().post(requestBody).url(url).build();
try {
Response response = okHttpClient.newCall(request).execute();
System.out.println(response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}

3、Delete请求示例

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public static void main(String[] args) {
String url = "http://zouchanglin.cn/info/remove";
OkHttpClient okHttpClient = new OkHttpClient();
RequestBody requestBody = new FormBody.Builder()
.add("id", "001002003004").build();
Request request = new Request.Builder()
.delete(requestBody).url(url).build();
try {
Response response = okHttpClient.newCall(request).execute();
System.out.println(response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}

4、附加请求头示例

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public static void main(String[] args) {
String url = "http://zouchanglin.cn/info/remove";
OkHttpClient okHttpClient = new OkHttpClient();
RequestBody requestBody = new FormBody.Builder()
.add("id", "001002003004").build();
Request request = new Request.Builder()
.delete(requestBody)
.addHeader("Accept", "application/vnd..")
.url(url).build();
try {
Response response = okHttpClient.newCall(request).execute();
System.out.println(response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}

5、请求异步回调示例

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public static void main(String[] args) {
String url = "http://zouchanglin.cn/info/remove";
OkHttpClient okHttpClient = new OkHttpClient();
RequestBody requestBody = new FormBody.Builder()
.add("id", "0010003004").build();
Request request = new Request.Builder().delete(requestBody).url(url).build();
Call call = okHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
//TODO...
}

@Override
public void onResponse(Call call, Response response) throws IOException {
//TODO...
}
});
}

6、上传文件加参数示例

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@PostMapping("upload")
public String uploadToRemoteHost(String ip, String path, String fileId) {
String url = String.format("http://%s:8080//api/host/file/create/", ip);
//找到文件对象
Optional<ImageFile> bigFileById = fileService.getBigFileById(fileId);
if(bigFileById.isPresent()){
ImageFile imageFile = bigFileById.get();
OkHttpClient okHttpClient = new OkHttpClient();
MultipartBody.Builder requestBody = new MultipartBody.Builder();
requestBody.setType(MultipartBody.FORM);
RequestBody body = RequestBody.create(
MediaType.parse("application/octet-stream"),
imageFile.getContent().getData());

// 参数分别为 请求key 文件名称 RequestBody
requestBody.addFormDataPart("file", imageFile.getName(), body);
//要上传的文字参数
Map<String, String> map = new HashMap<>();
map.put("name", imageFile.getName());
map.put("path", path);
for (String key : map.keySet()) {
requestBody.addFormDataPart(key, map.get(key));
}
MultipartBody build = requestBody.build();
try {
Request request = new Request.Builder().post(build).url(url).build();
Response execute = okHttpClient.newCall(request).execute();
if(execute.isSuccessful()){
return execute.body().string();
}
return JSONObject.toJSONString(ResultVOUtil.error(1, "网络错误"));
} catch (IOException e) {
e.printStackTrace();
return JSONObject.toJSONString(ResultVOUtil.error(2, "网络错误2"));
}
}
return JSONObject.toJSONString(ResultVOUtil.error(3, "文件不存在"));
}

7、下载文件示例

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public void downloadImg(View view){
OkHttpClient client = new OkHttpClient();
final Request request = new Request.Builder().get()
.url("http://wwwx.yyy/a.png")
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
Log.e("moer", "onFailure: ");;
}

@Override
public void onResponse(Call call, Response response) throws IOException {
//拿到字节流
InputStream is = response.body().byteStream();

int len = 0;
File file = new File(Environment.getExternalStorageDirectory(), "n.png");
FileOutputStream fos = new FileOutputStream(file);
byte[] buf = new byte[128];

while ((len = is.read(buf)) != -1){
fos.write(buf, 0, len);
}

fos.flush();
//关闭流
fos.close();
is.close();
}
});
}

8、OkHttp的坑

OkHttp请求回调中response.body().string()只能有效调用一次,调用response.body().string()的时候数据流已经关闭了,再次调用就是提示已经closed,抛出java.lang.IllegalStateException: closed异常,所以这个坑还是有点大,我在debug的时候由于已经监视了一次response.body().string()的返回值,在代码中跑完就是IllegalStateException。 调试代码调试时,表达式的监视有时候会影响代码的运行,比如就像OkHttp这种情况。

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