HttpURLConnection
tags:java
HTTP get/post请求
/**
* This class encapsulates methods for requesting a server via HTTP GET/POST and
* provides methods for parsing response from the server.
* @author www.codejava.net
*/
public class HttpUtility {
/**
* Represents an HTTP connection
*/
private static HttpURLConnection httpConn;
/**
* Makes an HTTP request using GET method to the specified URL.
*
* @param requestURL the URL of the remote server
* @return An HttpURLConnection object
* @throws IOException thrown if any I/O error occurred
*/
public static HttpURLConnection sendGetRequest(String requestURL)
throws IOException {
URL url = new URL(requestURL);
httpConn = (HttpURLConnection) url.openConnection();
httpConn.setUseCaches(false);
httpConn.setDoInput(true); // true if we want to read server's response
httpConn.setDoOutput(false); // false indicates this is a GET request
return httpConn;
}
/**
* Makes an HTTP request using POST method to the specified URL.
*
* @param requestURL the URL of the remote server
* @param params A map containing POST data in form of key-value pairs
* @return An HttpURLConnection object
* @throws IOException thrown if any I/O error occurred
*/
public static HttpURLConnection sendPostRequest(String requestURL,
Map<String, String> params) throws IOException {
URL url = new URL(requestURL);
httpConn = (HttpURLConnection) url.openConnection();
httpConn.setUseCaches(false);
httpConn.setDoInput(true); // true indicates the server returns response
StringBuffer requestParams = new StringBuffer();
if (params != null && params.size() > 0) {
httpConn.setDoOutput(true); // true indicates POST request
// creates the params string, encode them using URLEncoder
for (String key : params.keySet()) {
String value = params.get(key);
requestParams.append(URLEncoder.encode(key, "UTF-8"));
requestParams.append("=").append(
URLEncoder.encode(value, "UTF-8"));
requestParams.append("&");
}
// sends POST data
OutputStreamWriter writer = new OutputStreamWriter(
httpConn.getOutputStream());
writer.write(requestParams.toString());
writer.flush();
}
return httpConn;
}
/**
* Returns only one line from the server's response. This method should be
* used if the server returns only a single line of String.
*
* @return a String of the server's response
* @throws IOException thrown if any I/O error occurred
*/
public static String readSingleLineRespone() throws IOException {
InputStream inputStream = null;
if (httpConn != null) {
inputStream = httpConn.getInputStream();
} else {
throw new IOException("Connection is not established.");
}
BufferedReader reader = new BufferedReader(new InputStreamReader(
inputStream));
String response = reader.readLine();
reader.close();
return response;
}
/**
* Returns an array of lines from the server's response. This method should
* be used if the server returns multiple lines of String.
*
* @return an array of Strings of the server's response
* @throws IOException thrown if any I/O error occurred
*/
public static String[] readMultipleLinesRespone() throws IOException {
InputStream inputStream = null;
if (httpConn != null) {
inputStream = httpConn.getInputStream();
} else {
throw new IOException("Connection is not established.");
}
BufferedReader reader = new BufferedReader(new InputStreamReader(
inputStream));
List<String> response = new ArrayList<String>();
String line = "";
while ((line = reader.readLine()) != null) {
response.add(line);
}
reader.close();
return response.toArray(new String[0]);
}
/**
* Closes the connection if opened
*/
public static void disconnect() {
if (httpConn != null) {
httpConn.disconnect();
}
}
public static void main(String[] args) {
// test sending GET request
String requestURL = "http://www.google.com";
try {
HttpUtility.sendGetRequest(requestURL);
String[] response = HttpUtility.readMultipleLinesRespone();
for (String line : response) {
System.out.println(line);
}
} catch (IOException ex) {
ex.printStackTrace();
}
HttpUtility.disconnect();
System.out.println("=====================================");
// test sending POST request
Map<String, String> params = new HashMap<>();
requestURL = "https://accounts.google.com/ServiceLoginAuth";
params.put("Email", "your_email");
params.put("Passwd", "your_password");
try {
HttpUtility.sendPostRequest(requestURL, params);
String[] response = HttpUtility.readMultipleLinesRespone();
for (String line : response) {
System.out.println(line);
}
} catch (IOException ex) {
ex.printStackTrace();
}
HttpUtility.disconnect();
}
}
HttpURLConnection 下载
/**
* A utility that downloads a file from a URL.
*
* @author www.codejava.net
*/
public class HttpURLDownloadUtility {
private static final int BUFFER_SIZE = 4096;
/**
* Downloads a file from a URL
*
* @param fileURL HTTP URL of the file to be downloaded
* @param saveDir path of the directory to save the file
* @throws IOException
*/
public static void downloadFile(String fileURL, String saveDir)
throws IOException {
URL url = new URL(fileURL);
HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
int responseCode = httpConn.getResponseCode();
// always check HTTP response code first
if (responseCode == HttpURLConnection.HTTP_OK) {
String fileName = "";
String disposition = httpConn.getHeaderField("Content-Disposition");
String contentType = httpConn.getContentType();
int contentLength = httpConn.getContentLength();
if (disposition != null) {
// extracts file name from header field
int index = disposition.indexOf("filename=");
if (index > 0) {
fileName = disposition.substring(index + 10,
disposition.length() - 1);
}
} else {
// extracts file name from URL
fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1,
fileURL.length());
}
System.out.println("Content-Type = " + contentType);
System.out.println("Content-Disposition = " + disposition);
System.out.println("Content-Length = " + contentLength);
System.out.println("fileName = " + fileName);
// opens input stream from the HTTP connection
InputStream inputStream = httpConn.getInputStream();
String saveFilePath = saveDir + File.separator + fileName;
// opens an output stream to save into file
FileOutputStream outputStream = new FileOutputStream(saveFilePath);
int bytesRead = -1;
byte[] buffer = new byte[BUFFER_SIZE];
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
System.out.println("File downloaded");
} else {
System.out.println("No file to download. Server replied HTTP code: " + responseCode);
}
httpConn.disconnect();
}
public static void main(String[] args) {
String fileURL = "https://gss0.baidu.com/9vo3dSag_xI4khGko9WTAnF6hhy/zhidao/pic/item/4bed2e738bd4b31cce921fea8cd6277f9e2ff831.jpg";
String saveDir = "E:/download";
try {
downloadFile(fileURL, saveDir);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
HttpURLConnection上传
/**
* This utility class provides an abstraction layer for sending multipart HTTP
* POST requests to a web server.
*
* @author www.codejava.net
*/
public class MultipartUtility {
private String boundary;
private static final String LINE_FEED = "\r\n";
private HttpURLConnection httpConn;
private String charset;
private OutputStream outputStream;
private PrintWriter writer;
/**
* This constructor initializes a new HTTP POST request with content type
* is set to multipart/form-data
*
* @param requestURL
* @param charset
* @throws IOException
*/
public MultipartUtility(String requestURL, String charset)
throws IOException {
this.charset = charset;
// creates a unique boundary based on time stamp
boundary = "===" + System.currentTimeMillis() + "===";
boundary = "==" + UUID.randomUUID() + "==";
URL url = new URL(requestURL);
httpConn = (HttpURLConnection) url.openConnection();
httpConn.setUseCaches(false);
httpConn.setDoOutput(true); // indicates POST method
httpConn.setDoInput(true);
httpConn.setRequestProperty("Content-Type",
"multipart/form-data; boundary=" + boundary);
httpConn.setRequestProperty("User-Agent", "CodeJava Agent");
httpConn.setRequestProperty("Test", "Bonjour");
outputStream = httpConn.getOutputStream();
writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
true);
}
/**
* Adds a form field to the request
*
* @param name field name
* @param value field value
*/
public void addFormField(String name, String value) {
writer.append("--" + boundary).append(LINE_FEED);
writer.append("Content-Disposition: form-data; name=\"" + name + "\"")
.append(LINE_FEED);
writer.append("Content-Type: text/plain; charset=" + charset).append(
LINE_FEED);
writer.append(LINE_FEED);
writer.append(value).append(LINE_FEED);
writer.flush();
}
/**
* Adds a upload file section to the request
*
* @param fieldName name attribute in <input type="file" name="..." />
* @param uploadFile a File to be uploaded
* @throws IOException
*/
public void addFilePart(String fieldName, File uploadFile)
throws IOException {
String fileName = uploadFile.getName();
writer.append("--" + boundary).append(LINE_FEED);
writer.append(
"Content-Disposition: form-data; name=\"" + fieldName
+ "\"; filename=\"" + fileName + "\"")
.append(LINE_FEED);
writer.append(
"Content-Type: "
+ URLConnection.guessContentTypeFromName(fileName))
.append(LINE_FEED);
writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
writer.append(LINE_FEED);
writer.flush();
FileInputStream inputStream = new FileInputStream(uploadFile);
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
inputStream.close();
writer.append(LINE_FEED);
writer.flush();
}
/**
* Adds a header field to the request.
*
* @param name - name of the header field
* @param value - value of the header field
*/
public void addHeaderField(String name, String value) {
writer.append(name + ": " + value).append(LINE_FEED);
writer.flush();
}
/**
* Completes the request and receives response from the server.
*
* @return a list of Strings as response in case the server returned
* status OK, otherwise an exception is thrown.
* @throws IOException
*/
public List<String> finish() throws IOException {
List<String> response = new ArrayList<String>();
writer.append(LINE_FEED).flush();
writer.append("--" + boundary + "--").append(LINE_FEED);
writer.close();
// checks server's status code first
int status = httpConn.getResponseCode();
if (status == HttpURLConnection.HTTP_OK) {
BufferedReader reader = new BufferedReader(new InputStreamReader(
httpConn.getInputStream()));
String line = null;
while ((line = reader.readLine()) != null) {
response.add(line);
}
reader.close();
httpConn.disconnect();
} else {
throw new IOException("Server returned non-OK status: " + status);
}
return response;
}
public static void main(String[] args) {
String charset = "UTF-8";
File uploadFile1 = new File("e:/Test/PIC1.JPG");
File uploadFile2 = new File("e:/Test/PIC2.JPG");
String requestURL = "http://localhost:8080/FileUploadSpringMVC/uploadFile.do";
try {
MultipartUtility multipart = new MultipartUtility(requestURL, charset);
multipart.addHeaderField("User-Agent", "CodeJava");
multipart.addHeaderField("Test-Header", "Header-Value");
multipart.addFormField("description", "Cool Pictures");
multipart.addFormField("keywords", "Java,upload,Spring");
multipart.addFilePart("fileUpload", uploadFile1);
multipart.addFilePart("fileUpload", uploadFile2);
List<String> response = multipart.finish();
System.out.println("SERVER REPLIED:");
for (String line : response) {
System.out.println(line);
}
} catch (IOException ex) {
System.err.println(ex);
}
}
}
