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Spark HistoryServer之Jetty简单使用
这两天在看Spark HistoryServer的代码，发现里面使用了Jetty，下面简单描述下Jetty的使用
有两个Servlet：HelloServlet和WorldServlet
package com.luogankun.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class HelloServlet extends HttpServlet { private static final long serialVersionUID = 1L; private String msg = "hello"; public HelloServlet() { } public HelloServlet(String msg) { this.msg = "hello: "+ msg; } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().println(msg); } }
package com.luogankun.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class WorldServlet extends HttpServlet{ private static final long serialVersionUID = 1L; private String msg = "world"; public WorldServlet() { } public WorldServlet(String msg) { this.msg = "world: " + msg; } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().println(msg); }}
Jetty客户端测试：
package com.luogankun.jetty;import org.eclipse.jetty.server.Server;import org.eclipse.jetty.servlet.ServletContextHandler;import org.eclipse.jetty.servlet.ServletHolder;import com.luogankun.servlet.HelloServlet;import com.luogankun.servlet.WorldServlet;public class JettyServer { public static void main(String[] args) throws Exception { Server server = new Server(7798); //指定jettyserver的启动端口 ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS); context.setContextPath("/"); //设置访问路径 server.setHandler(context); // http://localhost:8080/hello context.addServlet(new ServletHolder(new HelloServlet()), "/hello"); //当访问/hello时执行HelloServlet() // http://localhost:8080/hello/luogankun context.addServlet(new ServletHolder(new HelloServlet("luogankun")),"/hello/luogankun"); //当执行/hello/luogankun时执行HelloServlet // http://localhost:8080/world context.addServlet(new ServletHolder(new WorldServlet()), "/world"); //当执行/world时执行WorldServlet // http://localhost:8080/world/luogankun context.addServlet(new ServletHolder(new WorldServlet("luogankun")), "/world/luogankun"); //当执行/world/luogankun时执行WorldServlet server.start(); server.join(); }}
总结：当request请求匹配到某个设定的路径时就执行某个指定的Servlet。
在浏览器中访问如下地址，注意观察执行结果
http://localhost:8080/hello
http://localhost:8080/hello/luogankun
http://localhost:8080/world
http://localhost:8080/world/luogankun
查看HistoryServer的代码
def initialize() { attachPage(new HistoryPage(this)) attachHandler(createStaticHandler(SparkUI.STATIC_RESOURCE_DIR, "/static")) val contextHandler = new ServletContextHandler contextHandler.setContextPath(HistoryServer.UI_PATH_PREFIX) //UI_PATH_PREFIX是history contextHandler.addServlet(new ServletHolder(loaderServlet), "/*") attachHandler(contextHandler)}private val loaderServlet = new HttpServlet { protected override def doGet(req: HttpServletRequest, res: HttpServletResponse): Unit = { val parts = Option(req.getPathInfo()).getOrElse("").split("/") if (parts.length < 2) { res.sendError(HttpServletResponse.SC_BAD_REQUEST, ......)}") return } val appId = parts(1) appCache.get(appId) res.sendRedirect(res.encodeRedirectURL(req.getRequestURI())) }}
可以看到当请求为: /history/*时交由loadServlet执行，该步骤在historyserver主页中点击查看某个app历史信息时触发；
此处的req.getPathInfo()的值为/app编号，形如：/app-20141105100235-0009
刚开始看代码时，不懂jetty，死活弄不明白怎么跳转过到具体的app信息页面的，了解下jetty后明白了是按照指定的请求路径进行转发的。
Spark HistoryServer之Jetty简单使用
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