JSP EL表达式使用
2015-10-30 08:45
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JSP EL表达式使用：
Servlet:
JSP:
JSP转换生成的Java：
Servlet:
package com.stono.servlet;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.stono.servlet.bean.Dog;
import com.stono.servlet.bean.Person;
import com.stono.servlet.bean.Toy;
public class TestServlet6 extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Person person = new Person();
Dog dog = new Dog();
Toy toy = new Toy();
toy.setName("toyName");
dog.setName("dogName");
dog.setToy(toy);
person.setDog(dog);
person.setName("personName");
req.setAttribute("person", person);
String[] musics = new String[] { "m1", "m2", "m3" };
req.setAttribute("musics", musics);
Map<String, Object> map = new HashMap<String, Object>();
map.put("a", "ma");
map.put("b", "mb");
map.put("c", "mc");
req.setAttribute("map", map);
Map<String, Object> map2 = new HashMap<String, Object>();
map2.put("a", "m2a");
req.setAttribute("map2", map2);
req.setAttribute("aref", "a");
RequestDispatcher dispatcher = req.getRequestDispatcher("index016.jsp");
dispatcher.forward(req, resp);
}
}JSP:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
pageContext.setAttribute("pca", "pageContextAttribute");
//session.setAttribute("s", "session");
%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>016</title>
</head>
<body>
<p>JSP生成的java文件中，EL表达式使用统一的方式进行数据读取；</p>
<p>EL result is : ${pageScope.pca }</p>
<p>person.name is : ${person.name }</p>
<p>person.dog.name is : ${person.dog.name }</p>
<p>musics[0] is : ${musics[0]}</p>
<p>musics["1"] is : ${musics["1"]}</p>
<p>musics["2"] is : ${musics[1+1]}</p>
<p>map[a] is : ${map[a] }</p>
<p>map["a"] is : ${map["a"] }</p>
<p>map.a is : ${map.a }</p>
<p>[]中没有引号，就会计算括号中的内容：</p>
<p>map2[aref] is : ${map2[aref] }</p>
<p>map2["aref"] is : ${map2["aref"] }</p>
<p>person.dog.toy.name is : ${person.dog.toy.name}</p>
<p>XXX is : ${XXX }</p>
<p>
${pageScope }
${requestScope }
${sessionScope }
${applicationScope }
${param }
${paramValues }
${header }
${headerValues }
${cookie }
${initParam }
${pageContext }
</p>
</body>
</html>JSP转换生成的Java：
/*
* Generated by the Jasper component of Apache Tomcat
* Version: Apache Tomcat/7.0.35
* Generated at: 2015-10-30 00:31:49 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.*;
public final class index016_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 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');
out.write('\n');
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
pageContext.setAttribute("pca", "pageContextAttribute");
//session.setAttribute("s", "session");
out.write("\r\n");
out.write("<!DOCTYPE html>\r\n");
out.write("<html>\r\n");
out.write("<head>\r\n");
out.write("<meta charset=\"UTF-8\">\r\n");
out.write("<title>016</title>\r\n");
out.write("</head>\r\n");
out.write("<body>\r\n");
out.write("\t<p>EL result is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${pageScope.pca }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>person.name is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${person.name }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>person.dog.name is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${person.dog.name }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>musics[0] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${musics[0]}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>musics[\"1\"] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${musics[\"1\"]}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>musics[\"2\"] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${musics[1+1]}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>map[a] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${map[a] }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>map[\"a\"] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${map[\"a\"] }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>map.a is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${map.a }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>[]中没有引号，就会计算括号中的内容：</p>\r\n");
out.write("\t<p>map2[aref] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${map2[aref] }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>map2[\"aref\"] is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${map2[\"aref\"] }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>person.dog.toy.name is : ");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${person.dog.toy.name}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("</p>\r\n");
out.write("\t<p>\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${pageScope }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${requestScope }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${sessionScope }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${applicationScope }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${param }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${paramValues }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${header }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${headerValues }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${cookie }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${initParam }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t\t");
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${pageContext }", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false));
out.write("\r\n");
out.write("\t</p>\r\n");
out.write("</body>\r\n");
out.write("</html>\r\n");
} catch (java.lang.Throwable t) {
if (!(t instanceof javax.servlet.jsp.SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
try { 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);
}
}
}
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