JSP userBean setProperty getProperty指令使用

javaBean的属性取决于get/set方法，而不是真实的属性名称。

jsp文件：

<%@ 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");

%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>009index</title>

</head>

<body>

    <jsp:useBean id="person" class="com.stono.servlet.bean.Person">

        <jsp:setProperty property="name" name="person" value="stono" />

    </jsp:useBean>

    <jsp:getProperty property="name" name="person" />

</body>

</html>

转换的java文件：

/*

 * Generated by the Jasper component of Apache Tomcat

 * Version: Apache Tomcat/7.0.35

 * Generated at: 2015-10-20 04:32:26 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 index009_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");

      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>009index</title>\r\n");

      out.write("</head>\r\n");

      out.write("<body>\r\n");

      out.write("\t");

      com.stono.servlet.bean.Person person = null;

      person = (com.stono.servlet.bean.Person) _jspx_page_context.getAttribute("person", javax.servlet.jsp.PageContext.PAGE_SCOPE);

      if (person == null){

        person = new com.stono.servlet.bean.Person();

        _jspx_page_context.setAttribute("person", person, javax.servlet.jsp.PageContext.PAGE_SCOPE);

        out.write("\r\n");

        out.write("\t\t");

        org.apache.jasper.runtime.JspRuntimeLibrary.introspecthelper(_jspx_page_context.findAttribute("person"), "name", "stono", null, null, false);

        out.write('\r');

        out.write('\n');

        out.write('    ');

      }

      out.write('\r');

      out.write('\n');

      out.write('    ');

      out.write(org.apache.jasper.runtime.JspRuntimeLibrary.toString((((com.stono.servlet.bean.Person)_jspx_page_context.findAttribute("person")).getName())));

      out.write("\r\n");

      out.write("\t\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);

    }

  }

}

JavaBean：

package com.stono.servlet.bean;

public class Person {

    // 对外的属性名称还是name，

    private String name2;

    public String getName() {

        return name2;

    }

    public void setName(String name) {

        this.name2 = name;

    }

}

jsp:userBean的使用：

<%@ 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");

%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>009index</title>

</head>

<body>

    <p>

        jsp:useBean id="person" class="com.stono.servlet.bean.Person",如果Person是抽象类，会有异常：

        <pre>

            严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [/index013.jsp (line: 14, column: 1) The value for the useBean class attribute com.stono.servlet.bean.Person is invalid.] with root cause

            org.apache.jasper.JasperException: /index013.jsp (line: 14, column: 1) The value for the useBean class attribute com.stono.servlet.bean.Person is invalid.

        </pre>

    </p>

    <p>

        对于抽象类需要使用jsp:useBean id="person" type="com.stono.servlet.bean.Person" class="com.stono.servlet.bean.Employee"进行使用。

    </p>

    <jsp:useBean id="person" type="com.stono.servlet.bean.Person" class="com.stono.servlet.bean.Employee">

        <jsp:setProperty property="name" name="person" value="stono" />

    </jsp:useBean>

    <jsp:getProperty property="name" name="person" />

    <p>

        直接输入jsp:useBean id="person2" type="com.stono.servlet.bean.Person"会报错：

        <pre>

            严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [javax.servlet.ServletException: java.lang.InstantiationException: bean person2 not found within scope] with root cause

            java.lang.InstantiationException: bean person2 not found within scope

        </pre>

        输入jsp:useBean id="person" type="com.stono.servlet.bean.Person"也是有问题的：

        <pre>

            严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [/index013.jsp (line: 35, column: 1) useBean: Duplicate bean name: {0}] with root cause

            org.apache.jasper.JasperException: /index013.jsp (line: 35, column: 1) useBean: Duplicate bean name: {0}

        </pre>

    </p>

    <p>

        在servlet中进行request.setAttribute("person3",person3),但是在jsp中直接写：jsp:useBean id="person3" type="com.stono.servlet.bean.Person"会报错：

        <pre>

            严重: Servlet.service() for servlet jsp threw exception

            java.lang.InstantiationException: bean person3 not found within scope

        </pre>

        因为默认的scope是page；修改为scope="request"，就可以读取到request传递过来的值；

    </p>

    <p>

        如果希望使用jsp:useBean id="person3" type="com.stono.servlet.bean.Person",还不能在scriplet中使用名称为person3的变量，需要如下定义使用：

        <pre>

            &lt;%@ page import="com.stono.servlet.bean.*" %&gt;

            &lt;%

                Person person33 = new Employee();

                person33.setName("stono3inJsp");

                pageContext.setAttribute("person3", person33);

            %&gt

            &lt;jsp:useBean id="person3" type="com.stono.servlet.bean.Person"&gt&lt;/jsp:useBean&gt

            &lt;jsp:getProperty property="name" name="person3"/&gt

        </pre>

    </p>

</body>

</html>

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