00-03、從JSP開始 · 淺入淺出Java Web

## 創建web項目打開netbeans，在菜單欄依次選擇“File”、“New Project...”，然后 1、選擇java web： [![](https://box.kancloud.cn/2015-10-17_5621d5df8d4db.png)](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/00-03/01.png) 2、項目名稱、路徑： [![](https://box.kancloud.cn/2015-10-17_5621d5dfae489.png)](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/00-03/02.png) 3、選擇使用的web容器，編寫ContextPath： [![](https://box.kancloud.cn/2015-10-17_5621d5dfbbb6a.png)](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/00-03/03.png) 生成的web項目結構如下： [![](https://box.kancloud.cn/2015-10-17_5621d5dfcc8e5.png)](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/00-03/04.png) index.html的內容如下： ~~~ <!DOCTYPE html>  <html> <head> <title>TODO supply a title</title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> </head> <body> <div>TODO write content</div> </body> </html> ~~~ `context.xml`的內容如下： ~~~ <?xml version="1.0" encoding="UTF-8"?> <Context antiJARLocking="true" path="/HelloJSP"/> ~~~ `apache-tomcat-8.0.15/conf/server.xml`中關于端口的配置如下： ~~~ <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> ~~~ 運行項目后，netbeans的輸出信息如下： ~~~ ant -f /data/Code/netbeans/HelloJSP -Dnb.internal.action.name=run -Ddirectory.deployment.supported=true -DforceRedeploy=false -Dnb.wait.for.caches=true -Dbrowser.context=/data/Code/netbeans/HelloJSP run init: deps-module-jar: deps-ear-jar: deps-jar: library-inclusion-in-archive: library-inclusion-in-manifest: compile: compile-jsps: Incrementally deploying http://localhost:8084/HelloJSP Completed incremental distribution of http://localhost:8084/HelloJSP run-deploy: Browsing: http://localhost:8084/HelloJSP run-display-browser: run: ~~~ 使用瀏覽器訪問`http://localhost:8084/HelloJSP/`，能看到`TODO write content`。 **那么問題來了，為什么配置的是8080,訪問時卻用8084端口？** 答案是：這個端口是netbeans啟動tomcat時配置的。看一下啟動命令： ~~~ $ ps -ef | grep 'tomcat' | grep -v grep letian 390 24314 0 09:24 ? 00:00:08 /data/Apps/jdk1.8.0_20/bin/java -Djava.util.logging.config.file=/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Dhttp.nonProxyHosts=localhost|127.0.0.1|myhost -Djava.endorsed.dirs=/data/Apps/apache-tomcat-8.0.15/endorsed -classpath /data/Apps/apache-tomcat-8.0.15/bin/bootstrap.jar:/data/Apps/apache-tomcat-8.0.15/bin/tomcat-juli.jar -Dcatalina.base=/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base -Dcatalina.home=/data/Apps/apache-tomcat-8.0.15 -Djava.io.tmpdir=/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/temp org.apache.catalina.startup.Bootstrap start $ grep -r '8084' /home/letian/.netbeans/8.0.2 # 可以看到很多結果 ... ~~~ 也就是說，實際使用的是`/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/conf`?下的配置。在``/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/conf/Catalina/localhost/HelloJSP.xml`中有以下內容： ~~~ <Context antiJARLocking="true" docBase="/data/Code/netbeans/HelloJSP/build/web" path="/HelloJSP"/> ~~~ 這意味著訪問`http://localhost:8084/HelloJSP/`時對應的web應用部署在HelloJSP項目的`build/web/`目錄下。 ## [](https://github.com/someus/another-tutorial-about-java-web/blob/master/00-03.md#基于jsp的hello-world)基于JSP的hello world 刪除index.html，新建index.jsp，內容如下： ~~~ <%@page contentType="text/html" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>JSP Page</title> </head> <body> <% String data="hello world"; boolean flag=true; if (flag==true) { out.println("<h1>" +data.toUpperCase()+ "</h1>"); } %> </body> </html> ~~~ 運行項目，訪問`http://localhost:8084/HelloJSP/`，可以看到`HELLO WORLD`。 JSP在部署時會被轉換成servlet，`/home/letian/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/work/Catalina/localhost/HelloJSP/org/apache/jsp`中的`index_jsp.java`就是對應的servlet。其內容如下： ~~~ /* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/8.0.15 * Generated at: 2015-09-18 02:43:43 UTC * Note: The last modified time of this file was set to * the last modified time of the source file after * generation to assist with modification tracking. */ package org.apache.jsp; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent { private static final javax.servlet.jsp.JspFactory _jspxFactory = javax.servlet.jsp.JspFactory.getDefaultFactory(); private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants; private javax.el.ExpressionFactory _el_expressionfactory; private org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> getDependants() { return _jspx_dependants; } public void _jspInit() { _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); } public void _jspDestroy() { } public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response) throws java.io.IOException, javax.servlet.ServletException { final java.lang.String _jspx_method = request.getMethod(); if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) { response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD"); return; } final javax.servlet.jsp.PageContext pageContext; javax.servlet.http.HttpSession session = null; final javax.servlet.ServletContext application; final javax.servlet.ServletConfig config; javax.servlet.jsp.JspWriter out = null; final java.lang.Object page = this; javax.servlet.jsp.JspWriter _jspx_out = null; javax.servlet.jsp.PageContext _jspx_page_context = null; try { response.setContentType("text/html;charset=UTF-8"); pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true); _jspx_page_context = pageContext; application = pageContext.getServletContext(); config = pageContext.getServletConfig(); session = pageContext.getSession(); out = pageContext.getOut(); _jspx_out = out; out.write("\n"); out.write("<!DOCTYPE html>\n"); out.write("<html>\n"); out.write(" <head>\n"); out.write(" <meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\n"); out.write(" <title>JSP Page</title>\n"); out.write(" </head>\n"); out.write(" <body>\n"); out.write(" "); String data="hello world"; boolean flag=true; if (flag==true) { out.println("<h1>" +data.toUpperCase()+ "</h1>"); } out.write("\n"); out.write(" </body>\n"); out.write("</html>\n"); } catch (java.lang.Throwable t) { if (!(t instanceof javax.servlet.jsp.SkipPageException)){ out = _jspx_out; if (out != null && out.getBufferSize() != 0) try { if (response.isCommitted()) { out.flush(); } else { out.clearBuffer(); } } catch (java.io.IOException e) {} if (_jspx_page_context != null) _jspx_page_context.handlePageException(t); else throw new ServletException(t); } } finally { _jspxFactory.releasePageContext(_jspx_page_context); } } } ~~~ 感受一下這段代碼吧～關于JSP就介紹這么多。**需要記住的是：JSP最合適的用途是用作MVC中的視圖，而不是和HTML一起混合編碼（例如把從數據庫拉取數據也放入JSP中寫）** 要了解更多，請參考下面的相關資料。 ## [](https://github.com/someus/another-tutorial-about-java-web/blob/master/00-03.md#jsp相關資料)JSP相關資料 [JSP 教程](http://www.runoob.com/jsp/jsp-tutorial.html)