JDBC+Servlet+JSP整合开发之24.JSP指令元素

–JSP page指令
–JSP taglib指令
–JSP include指令

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? JSP page指令
– page指令的用途
? 为根据JSP页面生成的servlet指定高层的信息
– 能够控制
? 导入哪些类
?该servlet扩展哪个类
? 产生哪种MIME类型
? 如何处理多线程
? servlet是否共享会话
? 输出缓冲区的大小的行为
? 由哪个页面来处理意外的错误
– import属性
? 格式
– <%@ page import="package.class" %>
– <%@ page import="package.class1,...,package.classN" %>
? 目的
–在servlet定义的顶部生成导入语句
? 注意
– 尽管JSP页面几乎可以放在服务器的任何位置，但由JSP使用的类必须放在常规的servlet目录中
? 例如：
– …/WEB-INF/classes或
– …/WEB-INF/classes/directoryMatchingPackage

? 示例（代码）
–<%@ page import="java.util.*,com.amaker.*" %>

TestImport.java

User.java

TestImport.jsp

测试

看一下转换的Servlet文件哈~

TestImport_jsp.java

package org.apache.jsp;    

import javax.servlet.*;    
import javax.servlet.http.*;    
import javax.servlet.jsp.*;    
import java.util.*;    
import com.michael.jsp.*;    

public final class TestImport_jsp extends org.apache.jasper.runtime.HttpJspBase    
         implements org.apache.jasper.runtime.JspSourceDependent {    

     private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();    

     private static java.util.List _jspx_dependants;    

     private javax.el.ExpressionFactory _el_expressionfactory;    
     private org.apache.AnnotationProcessor _jsp_annotationprocessor;    

     public Object getDependants() {    
         return _jspx_dependants;    
    }    

     public void _jspInit() {    
        _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();    
        _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor. class.getName());    
    }    

     public void _jspDestroy() {    
    }    

     public void _jspService(HttpServletRequest request, HttpServletResponse response)    
                 throws java.io.IOException, ServletException {    

        PageContext pageContext = null;    
        HttpSession session = null;    
        ServletContext application = null;    
        ServletConfig config = null;    
        JspWriter out = null;    
        Object page = this;    
        JspWriter _jspx_out = null;    
        PageContext _jspx_page_context = null;    

         try {    
            response.setContentType( "text/html;charset=ISO-8859-1");    
            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");    

String path = request.getContextPath();    
String basePath = request.getScheme()+ "://"+request.getServerName()+":"+request.getServerPort()+path+"/";    

            out.write("\r\n");    
            out.write("\r\n");    
            out.write("//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");    
            out.write("\r\n");    
            out.write("    \r\n");    
            out.write("        );    
            out.print(basePath);    
            out.write("\">\r\n");    
            out.write("        \r\n");    
            out.write("        \r\n");    
            out.write("        \r\n");    
            out.write("\t\r\n");    
            out.write("\t\r\n");    
            out.write("\t        \r\n");    
            out.write("\t\r\n");    
            out.write("\t\r\n");    
            out.write("\t\r\n");    
            out.write("\r\n");    
            out.write("    \r\n");    
            out.write("    \r\n");    
            out.write("    \r\n");    
            out.write("        

Test Import!

\r\n");    
            out.write("        ");    
        List list = new ArrayList();    
        User u = new User();    
        u.setId(1);    
        u.setName("michael");    
        list.add(u);    
        for(int i=0;i                User u2 = (User) list.get(i);    
                out.println(u2.getId());    
                out.println(u2.getName());    
        }        
            out.write("\r\n");    
            out.write("    \r\n");    
            out.write("\r\n");    
        } catch (Throwable t) {    
            if (!(t instanceof 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);    
            }    
        } finally {    
            _jspxFactory.releasePageContext(_jspx_page_context);    
        }    
    }    
}

 
–contentType和pageEncoding属性
? 格式
–<%@ page contentType="MIME-Type" %>
–<%@ page contentType="MIME-Type;charset=Character-Set" %>
–<%@ page pageEncoding="Character-Set" %>
? 目的
–指定由JSP页面生成的servlet生成的页面的MIME类型
? 注意
–属性值不能在请求期间计算得出
–常见MIME类型的表格，参见介绍响应报头的章节
? 生成Excel电子表格
–<%@ page contentType="application/vnd.ms-excel" %>

默认ISO-8859-1字符编码不显示中文，如果要显示中文可以使用gbk或gb2312

看下效果：

我们也可以不使用PageEncoding，可以指定内容类型的同时指定字符编码

看下效果：

生成Excel电子表格

看下效果：

 

TestContentType_jsp.java

package org.apache.jsp;    

import javax.servlet.*;    
import javax.servlet.http.*;    
import javax.servlet.jsp.*;    
import java.util.*;    

public final class TestContentType_jsp extends org.apache.jasper.runtime.HttpJspBase    
         implements org.apache.jasper.runtime.JspSourceDependent {    

     private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();    

     private static java.util.List _jspx_dependants;    

     private javax.el.ExpressionFactory _el_expressionfactory;    
     private org.apache.AnnotationProcessor _jsp_annotationprocessor;    

     public Object getDependants() {    
         return _jspx_dependants;    
    }    

     public void _jspInit() {    
        _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();    
        _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor. class.getName());    
    }    

     public void _jspDestroy() {    
    }    

     public void _jspService(HttpServletRequest request, HttpServletResponse response)    
                 throws java.io.IOException, ServletException {    

        PageContext pageContext = null;    
        HttpSession session = null;    
        ServletContext application = null;    
        ServletConfig config = null;    
        JspWriter out = null;    
        Object page = this;    
        JspWriter _jspx_out = null;    
        PageContext _jspx_page_context = null;    

         try {    
            response.setContentType( "application/vnd.ms-excel;charset=gbk");    
            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");    

String path = request.getContextPath();    
String basePath = request.getScheme()+ "://"+request.getServerName()+":"+request.getServerPort()+path+"/";    

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

                    out.println("tQ1\tQ2\tQ3\tQ4\tTotal");    
                out.println("Apples\t78\t87\t92\t29\t=SUM(B8:E8)");    
                out.println("Oranges\t77\t86\t93\t30\t=SUM(B9:E9)");    
            out.write("\r\n");    
            out.write("\r\n");    
        } catch (Throwable t) {    
            if (!(t instanceof 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);    
            }    
        } finally {    
            _jspxFactory.releasePageContext(_jspx_page_context);    
        }    
    }    
}

–session属性
?格式
–<%@ page session="true" %> <%-- Default --%>
–<%@ page session="false" %>
?目的
–指定页面是不是会话的一部分
?注意
–默认地，它是属于会话
–如果网站的流量较大，可以节省服务器端的内存
–要想真正起到作用，所有的相关网页都必须这样做

– errorPage属性
? 格式
– <%@ page errorPage="Relative URL" %>
? 目的
– 指定一个JSP页面，抛出的任何异常如果未在当前页面内被捕获，则由该页面进行处理。

TestErrorPage.jsp

此程序错误为空指向异常

现在加一个错误转向页面

TestErrorPage.jsp

error.jsp

看下效果：

? 注意
– 指定的错误处理页面可以通过“exception”变量来访问所抛出的异常。
– web.xml文件允许我们指定适用于整个应用的错误页面，当任何确定的异常或确定的HTTP状态代码产生时，都会使用该页面来处理。
– errorPage属性仅用于指定特定页面的错误页面

web.xml

404.jsp

看下效果：

– isErrorPage属性
? 格式
– <%@ page isErrorPage="true" %>
– <%@ page isErrorPage="false" %> <%-- Default --%>
? 目的
– 标示当前页面是否可以作为其他JSP页面的错误页面。
? 注意
– 名为exception的新预定义变量会被创建，并能够在错误页面中对其进行访问
– 只能将其作为紧急备份；明确地处理尽可能多的各种异常
– 不要忘记一定要检查查询数据中的值是否缺失或异常

下面指定被处理页面的错误类型

error.jsp

看下效果：

? JSP taglib指令
–格式
? <%@ taglib uri=“” prefix=“”%>
–uri：自定义标签的uri
–prefix：标签前缀
–目的
?在当前页面导入自定义标签
–示例
?使用JSTL
– <%@ taglib uri=" http://java.sun.com/jsp/jstl/core" prefix="c" %>

TestTagLib.jsp

看下效果：

再看另一实例 TestTagLib.jsp

看下效果：

? JSP include指令
–格式
? <%@ include file="Relative URL" %>
–目的
?为了在多个页面重用JSP内容，且需要JSP页面能够影响主页面

Head.jsp

footer.jsp

main.jsp

看下结果：

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