Eclipse中JSP生成的class檔案去了哪裡？
阿新 • • 發佈：2020-07-08
JSP在請求的時候，會先轉化成Servlet（其實就是個java類），然後生成class檔案，再提供服務。 那麼生成的java、class檔案在哪呢？
首先應該瞭解的是Tomcat在Eclipse的對映關係：Tomcat的伺服器目錄配置
可以瞭解到，Tomcat在Eclipse中提供了三種位置配置選項：
1 Use workspace metadata 2 Use Tomcat installation 3 Use custom location
分別對應三種情況說一下，注意要把Server中釋出的目錄全部刪除，然後clean後才能修改該配置項。（示例如下：1、2、3、4、5）
1，如果Server Locations選擇了第一項：Use workspace metadata
伺服器目錄，即生成的位元組碼和java檔案所在的目錄。它在你的Eclipse的工作目錄中。（比如我的工作目錄是在D:\program2，那麼在該目錄下就可以看到這個.metadata目錄了。）
參考上面的配置目錄D:\program2\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
這就是Tomcat對映的目錄，在這個目錄中有一個work目錄和一個wtpwebapps目錄（wtpwebapps目錄則存放對應的部署資原始檔）
work目錄中順著：work\Catalina\localhost\專案名字\org\apache\jsp 就可以找到你的專案對應的java檔案和class檔案。
我的：D:\program2\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\work\Catalina\localhost\jsp_demo\org\apache\jsp
2.如果選擇的是第二項，Use Tomcat installation
如果勾選的use tomcat installation，那麼你的tomcat目錄將被選定為tomcat所安裝的目錄。
此時，觀察上面的：Server path在D:\apache-tomcat-9.0.36。很好找了！
注意要先訪問jsp後，才會生成.class檔案。上面的Server Locations選擇Use workspace metadata 也一樣，下面是，選擇第二個（Use Tomcat installation...）的截圖演示）：
另外，選擇第二個選項，代表Tomcat的部署目錄，這個也能解決訪問http://localhost:8080時，出現404。因為，啟動一個tomcat，我們自己的worspace是沒有相關的內容的（選擇第一個），訪問的話肯定會報404錯誤。
3.如果勾選第三項，Use custom location
目錄的結構與上面的類似，上面這兩個都是不可以修改的，要麼是workspace所在的目錄，要麼是tomcat的目錄。
選擇該項，可以自定義生成的空間。
JSP程式碼示例：
<%@ page import="java.util.Map"%> <%@ page import="java.util.HashMap"%> <%@page contentType="text/html;charset=UTF-8" language="java"%> <html> <head> <title>Insert title here</title> </head> <body> <%--練習 --%> <%--1.宣告類屬性 --%> <%!private Integer id; private String name; private static Map<String, Object> map;%> <%--2.宣告static靜態程式碼塊 --%> <%!static { map = new HashMap<String, Object>(); map.put("key1", "value1"); map.put("key2", "value2"); map.put("key3", "value3"); }%> <%--3.宣告類方法 --%> <%!public int abc() { return 12; }%> <%--4.宣告內部類 --%> <%!public static class A { private Integer id = 12; private String abc = "abc"; }%> <%--練習： 1.輸出整型 2.輸出浮點型 3.輸出字串 4.輸出物件 --%> <%=12%><br/> <%=12.12%><br/> <%="我是字串"%><br/> <%=map%><br/> <%=request.getParameter("username")%><br/> <%--練習 --%> <%--1.程式碼指令碼----if 語句 --%> <% int i=13; if(i==12){ %> <h1>哈哈哈，我來了！</h1> <% }else{ %> <h1>我走了</h1> <% } %> <br/> <%--2.程式碼指令碼----for 迴圈語句 --%> <table border="1" cellspacing="0"> <% for(int j=0;j<10;j++){ %> <tr> <td>第<%=j+1%>行</td> </tr> <% } %> </table> <%--3.翻譯後Java檔案中_jspService方法內的程式碼都可以寫 --%> <% String username=request.getParameter("username"); System.out.println("使用者名稱的請求引數值："+ username); %> </body> </html>
在生成.java檔案中，可以看到生成的java檔案：
/* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/9.0.36 * Generated at: 2020-07-08 11:04:29 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.*; import java.util.Map; import java.util.HashMap; public final class b_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent, org.apache.jasper.runtime.JspSourceImports { private Integer id; private String name; private static Map<String, Object> map; static { map = new HashMap<String, Object>(); map.put("key1", "value1"); map.put("key2", "value2"); map.put("key3", "value3"); } public int abc() { return 12; } public static class A { private Integer id = 12; private String abc = "abc"; } 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 static final java.util.Set<java.lang.String> _jspx_imports_packages; private static final java.util.Set<java.lang.String> _jspx_imports_classes; static { _jspx_imports_packages = new java.util.HashSet<>(); _jspx_imports_packages.add("javax.servlet"); _jspx_imports_packages.add("javax.servlet.http"); _jspx_imports_packages.add("javax.servlet.jsp"); _jspx_imports_classes = new java.util.HashSet<>(); _jspx_imports_classes.add("java.util.Map"); _jspx_imports_classes.add("java.util.HashMap"); } private volatile javax.el.ExpressionFactory _el_expressionfactory; private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> getDependants() { return _jspx_dependants; } public java.util.Set<java.lang.String> getPackageImports() { return _jspx_imports_packages; } public java.util.Set<java.lang.String> getClassImports() { return _jspx_imports_classes; } public javax.el.ExpressionFactory _jsp_getExpressionFactory() { if (_el_expressionfactory == null) { synchronized (this) { if (_el_expressionfactory == null) { _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); } } } return _el_expressionfactory; } public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() { if (_jsp_instancemanager == null) { synchronized (this) { if (_jsp_instancemanager == null) { _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); } } } return _jsp_instancemanager; } public void _jspInit() { } 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 { if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) { final java.lang.String _jspx_method = request.getMethod(); if ("OPTIONS".equals(_jspx_method)) { response.setHeader("Allow","GET, HEAD, POST, OPTIONS"); return; } if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) { response.setHeader("Allow","GET, HEAD, POST, OPTIONS"); response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允許 GET、POST 或 HEAD。Jasper 還允許 OPTIONS"); 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("\r\n"); out.write("\r\n"); out.write("\r\n"); out.write("<html>\r\n"); out.write("<head>\r\n"); out.write("<title>Insert title here</title>\r\n"); out.write("</head>\r\n"); out.write("<body>\r\n"); out.write("\t"); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write(' '); out.write('\r'); out.write('\n'); out.write('\r'); out.write('\n'); out.write(' '); out.print(12); out.write("<br/>\r\n"); out.write("\t"); out.print(12.12); out.write("<br/>\r\n"); out.write("\t\r\n"); out.write("\t"); out.print("我是字串"); out.write("<br/>\r\n"); out.write("\t"); out.print(map); out.write("<br/>\r\n"); out.write("\t"); out.print(request.getParameter("username")); out.write("<br/>\r\n"); out.write("\r\n"); out.write('\r'); out.write('\n'); out.write('\r'); out.write('\n'); out.write(' '); int i=13; if(i==12){ out.write("\r\n"); out.write("\t<h1>哈哈哈，我來了！</h1>\r\n"); out.write("\t"); }else{ out.write("\r\n"); out.write("\t<h1>我走了</h1>\r\n"); out.write("\t"); } out.write("\r\n"); out.write("\t<br/>\r\n"); out.write("\t\r\n"); out.write("\t"); out.write("\r\n"); out.write("\t<table border=\"1\" cellspacing=\"0\">\r\n"); out.write("\t"); for(int j=0;j<10;j++){ out.write("\r\n"); out.write("\t<tr>\r\n"); out.write("\t<td>第"); out.print(j+1); out.write("行</td>\r\n"); out.write("\t</tr>\r\n"); out.write("\t"); } out.write("\r\n"); out.write("\t</table>\r\n"); out.write('\r'); out.write('\n'); out.write(' '); String username=request.getParameter("username"); System.out.println("使用者名稱的請求引數值："+ username); out.write("\r\n"); out.write("\r\n"); out.write("</body>\r\n"); out.write("</html>"); } 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); } } }