Java tutorial
/* The contents of this file are subject to the license and copyright terms * detailed in the license directory at the root of the source tree (also * available online at http://fedora-commons.org/license/). */ package fedora.common.http; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.URL; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager; import org.apache.commons.httpclient.UsernamePasswordCredentials; import org.apache.commons.httpclient.auth.AuthScope; import org.apache.commons.httpclient.methods.GetMethod; /** * A general-purpose, connection-pooling HTTP Client. All methods are * thread-safe. Provides option for client to handle HTTP redirects * * @version $Id$ */ public class WebClient { /** Seconds to wait before a connection is established. */ public int TIMEOUT_SECONDS = 20; /** Seconds to wait while waiting for data over the socket (SO_TIMEOUT). */ public int SOCKET_TIMEOUT_SECONDS = 120; /** Maxiumum http connections per host */ public int MAX_CONNECTIONS_PER_HOST = 5; /** Maxiumum total http connections */ public int MAX_TOTAL_CONNECTIONS = 20; /** Whether to automatically follow HTTP redirects. */ public boolean FOLLOW_REDIRECTS = true; /** * Maximum number of redirects to follow per request if FOLLOW_REDIRECTS is * true. */ public int MAX_REDIRECTS = 3; /** * What the "User-Agent" request header should say. Default is null, which * indicates that the header should not be provided. */ public String USER_AGENT = null; private MultiThreadedHttpConnectionManager m_cManager; /** * The proxy configuration for the web client. */ private static ProxyConfiguration proxy = new ProxyConfiguration(); public WebClient() { configureConnectionManager(); } public WebClient(ProxyConfiguration configuration) { proxy = configuration; configureConnectionManager(); } private void configureConnectionManager() { m_cManager = new MultiThreadedHttpConnectionManager(); m_cManager.getParams().setDefaultMaxConnectionsPerHost(MAX_CONNECTIONS_PER_HOST); m_cManager.getParams().setMaxTotalConnections(MAX_TOTAL_CONNECTIONS); m_cManager.getParams().setConnectionTimeout(TIMEOUT_SECONDS * 1000); m_cManager.getParams().setSoTimeout(SOCKET_TIMEOUT_SECONDS * 1000); } public HttpClient getHttpClient(String hostOrUrl) throws IOException { return getHttpClient(hostOrUrl, null); } public HttpClient getHttpClient(String hostOrURL, UsernamePasswordCredentials creds) throws IOException { String host = null; if (hostOrURL != null) { if (hostOrURL.indexOf("/") != -1) { URL url = new URL(hostOrURL); host = url.getHost(); } else { host = hostOrURL; } } HttpClient client = new HttpClient(m_cManager); if (host != null && creds != null) { client.getState().setCredentials(new AuthScope(host, AuthScope.ANY_PORT), creds); client.getParams().setAuthenticationPreemptive(true); } if (proxy.isHostProxyable(host)) { client.getHostConfiguration().setProxy(proxy.getProxyHost(), proxy.getProxyPort()); if (proxy.hasValidCredentials()) { client.getState().setProxyCredentials( new AuthScope(proxy.getProxyHost(), proxy.getProxyPort(), null), new UsernamePasswordCredentials(proxy.getProxyUser(), proxy.getProxyPassword())); } } return client; } public HttpInputStream get(String url, boolean failIfNotOK) throws IOException { return get(url, failIfNotOK, null); } public HttpInputStream get(String url, boolean failIfNotOK, String user, String pass) throws IOException { UsernamePasswordCredentials creds = null; if (user != null && !user.equals("") && pass != null && !pass.equals("")) creds = new UsernamePasswordCredentials(user, pass); return get(url, failIfNotOK, creds); } /** * Get an HTTP resource with the response as an InputStream, given a URL. If * FOLLOW_REDIRECTS is true, up to MAX_REDIRECTS redirects will be followed. * Note that if credentials are provided, for security reasons they will * only be provided to the FIRST url in a chain of redirects. Note that if * the HTTP response has no body, the InputStream will be empty. The success * of a request can be checked with getResponseCode(). Usually you'll want * to see a 200. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html * for other codes. * * @param url * A URL that we want to do an HTTP GET upon * @param failIfNotOK * boolean value indicating if an exception should be thrown if we do * NOT receive an HTTP 200 response (OK) * @return HttpInputStream the HTTP response * @throws IOException */ public HttpInputStream get(String url, boolean failIfNotOK, UsernamePasswordCredentials creds) throws IOException { HttpClient client; GetMethod getMethod = new GetMethod(url); if (USER_AGENT != null) { getMethod.setRequestHeader("User-Agent", USER_AGENT); } if (creds != null && creds.getUserName() != null && creds.getUserName().length() > 0) { client = getHttpClient(url, creds); getMethod.setDoAuthentication(true); } else { client = getHttpClient(url); } HttpInputStream in = new HttpInputStream(client, getMethod, url); int status = in.getStatusCode(); if (failIfNotOK) { if (status != 200) { //if (followRedirects && in.getStatusCode() == 302){ if (FOLLOW_REDIRECTS && 300 <= status && status <= 399) { int count = 1; while (300 <= status && status <= 399 && count <= MAX_REDIRECTS) { if (in.getResponseHeader("location") == null) { throw new IOException("Redirect HTTP response provided no location header."); } url = in.getResponseHeader("location").getValue(); in.close(); getMethod = new GetMethod(url); if (USER_AGENT != null) { getMethod.setRequestHeader("User-Agent", USER_AGENT); } in = new HttpInputStream(client, getMethod, url); status = in.getStatusCode(); count++; } if (300 <= status && status <= 399) { in.close(); throw new IOException("Too many redirects"); } else if (status != 200) { in.close(); throw new IOException( "Request failed [" + in.getStatusCode() + " " + in.getStatusText() + "]"); } // redirect was successful! } else { try { throw new IOException( "Request failed [" + in.getStatusCode() + " " + in.getStatusText() + "]"); } finally { try { in.close(); } catch (Exception e) { System.err.println("Can't close InputStream: " + e.getMessage()); } } } } } return in; } public String getResponseAsString(String url, boolean failIfNotOK) throws IOException { return getResponseAsString(url, failIfNotOK, null); } public String getResponseAsString(String url, boolean failIfNotOK, UsernamePasswordCredentials creds) throws IOException { InputStream in = get(url, failIfNotOK, creds); // Convert the response into a String. try { BufferedReader reader = new BufferedReader(new InputStreamReader(in)); StringBuffer buffer = new StringBuffer(); String line = reader.readLine(); while (line != null) { buffer.append(line + "\n"); line = reader.readLine(); } return buffer.toString(); } finally { try { in.close(); } catch (Exception e) { System.err.println("Can't close InputStream: " + e.getMessage()); } } } }