使用Apache HttpClient的健壮HTTP
下面的部分内容来源于《Unlocking Android》一书：要了解HTTPClient，我们先看一下如何使用核心类来执行HTTP GET和POST方法请求，此处我们结合使用Apache的ResonseHandler和Android的Handler，在与用户界面不同的线程中发起网络请求。
// new a Handler to receive the response by HTTP request.
private final Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
mPrgressDialog.dismiss();
String result = msg.getData().getString("RESPONSE");
mOutput.setText(result);
};
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mButton = (Button) findViewById(R.id.btn);
mButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mOutput.setText("");
performRequest(url);
}
});
mOutput = (TextView) findViewById(R.id.output);
}
// perform HTTP request with HttpRequestHelper asynchronously.
private void performRequest(final String url) {
final ResponseHandler<String> responseHandler = HttpRequestHelper
.getResponseHandlerInstance(mHandler);
// show a ProgressDialog to represent that it is woring now, and it
// will dismiss after receiving response.
mPrgressDialog = ProgressDialog.show(this, "working...",
"performing HTTP request");
new Thread() {
public void run() {
HttpRequestHelper helper = new HttpRequestHelper(
responseHandler);
// use GET method
helper.performGet(url, null, null, null);
};
}.start();
}
/**
* Helper for HTTP request via GET or POST method.
*/
public final class HttpRequestHelper {
private static final int POST_TYPE = 1;
private static final int GET_TYPE = 2;
public static final String CONTENT_TYPE = "Content-Type";
public static final String MIME_FORM_ENCODED = "application/x-www-form-urlencoded";
public static final String MIME_TEXT_PLAIN = "text/plain";
private final ResponseHandler<String> mResponseHandler;
public HttpRequestHelper(ResponseHandler<String> responseHandler) {
mResponseHandler = responseHandler;
}
public void performGet(String url, String user, String pwd,
final Map<String, String> addtionalHeaders) {
performRequest(null, url, user, pwd, addtionalHeaders, null, GET_TYPE);
}
public void performPost(String contentType, String url, String user,
String pwd, Map<String, String> addtionalHeaders,
Map<String, String> params) {
performRequest(contentType, url, user, pwd, addtionalHeaders, params,
POST_TYPE);
}
public void performPost(String url, String user, String pwd,
Map<String, String> addtionalHeaders, Map<String, String> params) {
performRequest(MIME_FORM_ENCODED, url, user, pwd, addtionalHeaders,
params, POST_TYPE);
}
private void performRequest(String contentType, String url, String user,
String pwd, Map<String, String> headers,
Map<String, String> params, int requestType) {
DefaultHttpClient client = new DefaultHttpClient();
if (user != null && pwd != null) {
client.getCredentialsProvider().setCredentials(AuthScope.ANY,
new UsernamePasswordCredentials(user, pwd));
}
final Map<String, String> sendHeaders = new HashMap<String, String>();
if (headers != null && !headers.isEmpty()) {
sendHeaders.putAll(headers);
}
if (POST_TYPE == requestType) {
sendHeaders.put(CONTENT_TYPE, contentType);
}
if (!sendHeaders.isEmpty()) {
client.addRequestInterceptor(new HttpRequestInterceptor() {
public void process(HttpRequest request, HttpContext context)
throws HttpException, IOException {
for (String key : sendHeaders.keySet()) {
if (!request.containsHeader(key)) {
request.addHeader(key, sendHeaders.get(key));
}
}
}
});
}
if (POST_TYPE == requestType) {
HttpPost post = new HttpPost(url);
List<NameValuePair> nvps = null;
if (params != null && !params.isEmpty()) {
nvps = new ArrayList<NameValuePair>();
for (String key : params.keySet()) {
nvps.add(new BasicNameValuePair(key, params.get(key)));
}
}
if (nvps != null) {
try {
post.setEntity(new UrlEncodedFormEntity(nvps));
} catch (UnsupportedEncodingException e) {
// TODO: handle exception
}
}
execute(client, post);
} else if (GET_TYPE == requestType) {
execute(client, new HttpGet(url));
}
}
private void execute(HttpClient client, HttpRequestBase method) {
try {
client.execute(method, mResponseHandler);
} catch (Exception e) {
BasicHttpResponse erroResponse = new BasicHttpResponse(
new ProtocolVersion("HTTP_ERROR", 1, 1), 500, "ERROR");
erroResponse.setReasonPhrase(e.getMessage());
try {
mResponseHandler.handleResponse(erroResponse);
} catch (Exception e2) {
// TODO: handle exception
}
}
}
public static ResponseHandler<String> getResponseHandlerInstance(
final Handler handler) {
return new ResponseHandler<String>() {
public String handleResponse(HttpResponse response)
throws ClientProtocolException, IOException {
Message message = handler.obtainMessage();
Bundle data = new Bundle();
HttpEntity entity = response.getEntity();
String result = null;
if (entity != null) {
try {
result = EntityUtils.toString(entity);
data.putString("RESPONSE", result);
} catch (IOException e) {
data.putString("RESPONSE", "Error - " + e.getMessage());
}
} else {
StatusLine status = response.getStatusLine();
data.putString("RESPONSE",
"Error - " + status.getReasonPhrase());
}
message.setData(data);
message.sendToTarget();
return result;
}
};
}
}
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