THRIFT-1608 Allow servlet to be supplied TProcessor and TProtocolFact…

…ory after the init() method has finished

Patch: Kiril Raychev

git-svn-id: https://svn.apache.org/repos/asf/thrift/trunk@1351848 13f79535-47bb-0310-9956-ffa450edef68

lib/java/src/org/apache/thrift/server/TExtensibleServlet.java

@@ -0,0 +1,152 @@
+package org.apache.thrift.server;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Map;
+
+import javax.servlet.ServletConfig;
+import javax.servlet.ServletContext;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.thrift.TException;
+import org.apache.thrift.TProcessor;
+import org.apache.thrift.protocol.TProtocol;
+import org.apache.thrift.protocol.TProtocolFactory;
+import org.apache.thrift.transport.TIOStreamTransport;
+import org.apache.thrift.transport.TTransport;
+
+/**
+ * Servlet implementation class ThriftServer, that allows {@link TProcessor} and
+ * {@link TProtocolFactory} to be supplied after the {@link #init()} method has
+ * finished. <br>
+ * Subclasses must implement the abstract methods that return the TProcessor and
+ * two TProtocolFactory. Those methods are guaranteed to be called exactly once,
+ * and that {@link ServletContext} is available.
+ */
+public abstract class TExtensibleServlet extends HttpServlet {
+  private static final long serialVersionUID = 1L;
+
+  private TProcessor processor;
+
+  private TProtocolFactory inFactory;
+
+  private TProtocolFactory outFactory;
+
+  private Collection<Map.Entry<String, String>> customHeaders;
+
+  /**
+   * Returns the appropriate {@link TProcessor}. This will be called <b>once</b> just
+   * after the {@link #init()} method
+   * 
+   * @return
+   */
+  protected abstract TProcessor getProcessor();
+
+  /**
+   * Returns the appropriate in {@link TProtocolFactory}. This will be called
+   * <b>once</b> just after the {@link #init()} method
+   * 
+   * @return
+   */
+  protected abstract TProtocolFactory getInProtocolFactory();
+
+  /**
+   * Returns the appropriate out {@link TProtocolFactory}. This will be called
+   * <b>once</b> just after the {@link #init()} method
+   * 
+   * @return
+   */
+  protected abstract TProtocolFactory getOutProtocolFactory();
+
+  @Override
+  public final void init(ServletConfig config) throws ServletException {
+    super.init(config); //no-args init() happens here
+    this.processor = getProcessor();
+    this.inFactory = getInProtocolFactory();
+    this.outFactory = getOutProtocolFactory();
+    this.customHeaders = new ArrayList<Map.Entry<String, String>>();
+
+    if (processor == null) {
+      throw new ServletException("processor must be set");
+    }
+    if (inFactory == null) {
+      throw new ServletException("inFactory must be set");
+    }
+    if (outFactory == null) {
+      throw new ServletException("outFactory must be set");
+    }
+  }
+
+  /**
+   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
+   *      response)
+   */
+  @Override
+  protected void doPost(HttpServletRequest request, HttpServletResponse response)
+      throws ServletException, IOException {
+    TTransport inTransport = null;
+    TTransport outTransport = null;
+
+    try {
+      response.setContentType("application/x-thrift");
+
+      if (null != this.customHeaders) {
+	for (Map.Entry<String, String> header : this.customHeaders) {
+	  response.addHeader(header.getKey(), header.getValue());
+	}
+      }
+
+      InputStream in = request.getInputStream();
+      OutputStream out = response.getOutputStream();
+
+      TTransport transport = new TIOStreamTransport(in, out);
+      inTransport = transport;
+      outTransport = transport;
+
+      TProtocol inProtocol = inFactory.getProtocol(inTransport);
+      TProtocol outProtocol = inFactory.getProtocol(outTransport);
+
+      processor.process(inProtocol, outProtocol);
+      out.flush();
+    } catch (TException te) {
+      throw new ServletException(te);
+    }
+  }
+
+  /**
+   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
+   *      response)
+   */
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
+      throws ServletException, IOException {
+    doPost(req, resp);
+  }
+
+  public void addCustomHeader(final String key, final String value) {
+    this.customHeaders.add(new Map.Entry<String, String>() {
+      public String getKey() {
+	return key;
+      }
+
+      public String getValue() {
+	return value;
+      }
+
+      public String setValue(String value) {
+	return null;
+      }
+    });
+  }
+
+  public void setCustomHeaders(Collection<Map.Entry<String, String>> headers) {
+    this.customHeaders.clear();
+    this.customHeaders.addAll(headers);
+  }
+}