JDBC+Servlet+JSP整合开发之23.JSP脚本元素 推荐
2010-04-12 13:37
441 查看
–脚本元素的类型
–JSP声明
? JSP声明中JSP/servlet之间的对应
? JSP声明：示例
–JSP表达式
? JSP表达式中JSP/servlet的对应
? JSP表达式：示例
–JSP scriptlet（代码块）
? JSP代码块中JSP/servlet的对应
–JSP声明和预定义变量
–JSP处理的两个阶段
##############################################
首先我们看下JAVA中如何申明变量、如何申明方法及方法与方法之间如何调用的哈~
看下结果
下面如果我们用JSP来写这个程序如何写哈~
? 脚本元素的类型
–声明
? 格式：<%! code %>
? 逐字地插入到servlet类的定义体中，不在任何方法之内
–表达式
? 格式：<%= expression %>
? 求值并插入到servlet的输出中
? 也就是会产生类似于out.print(expression)的语句
–scriptlet （代码块）
? 格式：<% code %>
? 逐字地插入到servlet的_jspService方法中(由service调用)
? JSP声明
–格式
? <%! Java Code %>
–结果
? 代码被逐字地插入到servlet类的定义中，在任何现有方法以外
–示例
<%! private int someField = 5; %>
<%! private void someMethod(...) {...} %>
–设计上的考虑
? 字段当然有用，但对于方法而言，通常在单独的Java类中定义更好一些
–XML兼容的语法
? <jsp:declaration>Java Code</jsp:declaration>
–JSP声明中JSP/servlet之间的对应
?原始的JSP
?生成的servlet代码
–JSP声明：示例
? JSP表达式
–格式
? <%= Java Expression %>
–结果
? 表达式被求值，转换成字符串，将按照它在JSP页面中出现的位置插入到HTML页面中。
? 即，表达式放置在out.print内
–示例
?当前时间：<%= new java.util.Date() %>
? 您的主机名：<%= request.getRemoteHost() %>
–XML兼容的语法
? <jsp:expression>Java Expression</jsp:expression>
?在单个页面中不能混合使用不同的版本。如果使用jsp:expression就必须整个页面都使用XML
–JSP表达式中JSP/servlet的对应
?原始的JSP
?所产生的具有代表性的servlet代码
–JSP表达式：示例
看下效果
JSP页面都会转换成Servlet,我们来看下
declaration_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
public final class declaration_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
private String name = "michael";
private int age = 20;
private String print(){
return name+":"+age;
}
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");
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("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" \r\n");
out.write(" <title>Test declarationJspPage...</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body> \r\n");
out.write(" \t<!-- declare variable and method -->\r\n");
out.write(" ");
out.write("\r\n");
out.write(" \r\n");
out.write(" Name:");
out.print(name );
out.write("<br/>\r\n");
out.write(" Age:");
out.print(age );
out.write("<br/>\r\n");
out.write(" Name and age:");
out.print(print() );
out.write("\r\n");
out.write(" \r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
来看下计算器的实例
看下结果
字段当然有用，但对于方法而言，通常在单独的Java类中定义更好一些
Calculator.java
declaration.jsp
看下效果
再看一个页面被访问的次数
看下效果：
exception.jsp
看下结果
exception_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
public final class exception_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
String name = "michael";
public String getTime(){
return new Date().toLocaleString();
}
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');
out.write('\n');
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
out.write("\r\n");
out.write("\r\n");
out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" <base href=\"");
out.print(basePath);
out.write("\">\r\n");
out.write(" \r\n");
out.write(" <title>My JSP 'exception.jsp' starting page</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body>\r\n");
out.write(" Time1:");
out.print(new Date().toLocaleString() );
out.write("<br/>\r\n");
out.write(" \r\n");
out.write(" ");
out.write("\r\n");
out.write(" Name:");
out.print(name );
out.write("<br/>\r\n");
out.write(" Time2:");
out.print(getTime() );
out.write("<br/>\r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
? JSP scriptlet（代码块）
–格式
? <% Java Code %>
–结果
? 代码被逐字地插入到servlet的_jspService方法中
–示例
<%
String queryData = request.getQueryString();
out.println("Attached GET data: " + queryData);
%>
<% response.setContentType("text/plain"); %>
–XML兼容的语法
? <jsp:scriptlet>Java Code</jsp:scriptlet>
–JSP scriptlet（代码块）中JSP/servlet的对应
?原始的JSP
?所产生的具有代表性的servlet代码
Scriptlet.jsp
看下效果：
Scriptlet_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
public final class Scriptlet_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');
out.write('\n');
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
out.write("\r\n");
out.write("\r\n");
out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" <base href=\"");
out.print(basePath);
out.write("\">\r\n");
out.write(" \r\n");
out.write(" <title>My JSP 'Scriptlet.jsp' starting page</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body>\r\n");
out.write(" ");
if(Calendar.AM_PM==Calendar.AM){
out.println("Good morning!");
}else{
out.println("Good afternoon!");
}
out.println("<hr/>");
String queryString = request.getQueryString();
out.println(queryString);
out.println("<hr/>");
String name = request.getParameter("name");
out.println(name);
out.println("<br/>");
String age = request.getParameter("age");
out.println(age);
out.println("<br/>");
String blog = request.getParameter("blog");
out.println(blog);
out.write("\r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
? JSP声明和预定义变量
–问题
? 预定义变量(request, response, out, session, 等)是jspService方法中的局部变量。因而，由JSP声明定义的方法或辅助类中的方法都不能使用它们。怎么处理这种情况呢？
–解决方案：将它们作为参数传递，例如 <%!
private void someMethod(HttpSession s) {
doSomethingWith(s);
}
%>
<% someMethod(session); %>
–要注意：JspWriter的println方法抛出IOException异常
? 使用println的方法要使用“throws IOException”
? JSP处理的两个阶段
–JSP页面转换阶段
?页面被编译成Java类，所有的HTML标签和JSP标签被处理，来生成一个Servlet类，然而，脚本和表达式不被执行。
–请求处理阶段
?当客户端请求服务器时，处于请求处理阶段
?在该阶段脚本和表达式被执行##############################################
附件：http://down.51cto.com/data/2355528
–JSP声明
? JSP声明中JSP/servlet之间的对应
? JSP声明：示例
–JSP表达式
? JSP表达式中JSP/servlet的对应
? JSP表达式：示例
–JSP scriptlet（代码块）
? JSP代码块中JSP/servlet的对应
–JSP声明和预定义变量
–JSP处理的两个阶段
##############################################
首先我们看下JAVA中如何申明变量、如何申明方法及方法与方法之间如何调用的哈~
看下结果
下面如果我们用JSP来写这个程序如何写哈~
? 脚本元素的类型
–声明
? 格式：<%! code %>
? 逐字地插入到servlet类的定义体中，不在任何方法之内
–表达式
? 格式：<%= expression %>
? 求值并插入到servlet的输出中
? 也就是会产生类似于out.print(expression)的语句
–scriptlet （代码块）
? 格式：<% code %>
? 逐字地插入到servlet的_jspService方法中(由service调用)
? JSP声明
–格式
? <%! Java Code %>
–结果
? 代码被逐字地插入到servlet类的定义中，在任何现有方法以外
–示例
<%! private int someField = 5; %>
<%! private void someMethod(...) {...} %>
–设计上的考虑
? 字段当然有用，但对于方法而言，通常在单独的Java类中定义更好一些
–XML兼容的语法
? <jsp:declaration>Java Code</jsp:declaration>
–JSP声明中JSP/servlet之间的对应
?原始的JSP
?生成的servlet代码
–JSP声明：示例
? JSP表达式
–格式
? <%= Java Expression %>
–结果
? 表达式被求值，转换成字符串，将按照它在JSP页面中出现的位置插入到HTML页面中。
? 即，表达式放置在out.print内
–示例
?当前时间：<%= new java.util.Date() %>
? 您的主机名：<%= request.getRemoteHost() %>
–XML兼容的语法
? <jsp:expression>Java Expression</jsp:expression>
?在单个页面中不能混合使用不同的版本。如果使用jsp:expression就必须整个页面都使用XML
–JSP表达式中JSP/servlet的对应
?原始的JSP
?所产生的具有代表性的servlet代码
–JSP表达式：示例
看下效果
JSP页面都会转换成Servlet,我们来看下
declaration_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
public final class declaration_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
private String name = "michael";
private int age = 20;
private String print(){
return name+":"+age;
}
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");
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("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" \r\n");
out.write(" <title>Test declarationJspPage...</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body> \r\n");
out.write(" \t<!-- declare variable and method -->\r\n");
out.write(" ");
out.write("\r\n");
out.write(" \r\n");
out.write(" Name:");
out.print(name );
out.write("<br/>\r\n");
out.write(" Age:");
out.print(age );
out.write("<br/>\r\n");
out.write(" Name and age:");
out.print(print() );
out.write("\r\n");
out.write(" \r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
来看下计算器的实例
看下结果
字段当然有用，但对于方法而言，通常在单独的Java类中定义更好一些
Calculator.java
declaration.jsp
看下效果
再看一个页面被访问的次数
看下效果：
exception.jsp
看下结果
exception_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
public final class exception_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
String name = "michael";
public String getTime(){
return new Date().toLocaleString();
}
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');
out.write('\n');
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
out.write("\r\n");
out.write("\r\n");
out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" <base href=\"");
out.print(basePath);
out.write("\">\r\n");
out.write(" \r\n");
out.write(" <title>My JSP 'exception.jsp' starting page</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body>\r\n");
out.write(" Time1:");
out.print(new Date().toLocaleString() );
out.write("<br/>\r\n");
out.write(" \r\n");
out.write(" ");
out.write("\r\n");
out.write(" Name:");
out.print(name );
out.write("<br/>\r\n");
out.write(" Time2:");
out.print(getTime() );
out.write("<br/>\r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
? JSP scriptlet（代码块）
–格式
? <% Java Code %>
–结果
? 代码被逐字地插入到servlet的_jspService方法中
–示例
<%
String queryData = request.getQueryString();
out.println("Attached GET data: " + queryData);
%>
<% response.setContentType("text/plain"); %>
–XML兼容的语法
? <jsp:scriptlet>Java Code</jsp:scriptlet>
–JSP scriptlet（代码块）中JSP/servlet的对应
?原始的JSP
?所产生的具有代表性的servlet代码
Scriptlet.jsp
看下效果：
Scriptlet_jsp.java
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
public final class Scriptlet_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');
out.write('\n');
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
out.write("\r\n");
out.write("\r\n");
out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" <base href=\"");
out.print(basePath);
out.write("\">\r\n");
out.write(" \r\n");
out.write(" <title>My JSP 'Scriptlet.jsp' starting page</title>\r\n");
out.write(" \r\n");
out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
out.write("\t<meta http-equiv=\"expires\" content=\"0\"> \r\n");
out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
out.write("\t<!--\r\n");
out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
out.write("\t-->\r\n");
out.write("\r\n");
out.write(" </head>\r\n");
out.write(" \r\n");
out.write(" <body>\r\n");
out.write(" ");
if(Calendar.AM_PM==Calendar.AM){
out.println("Good morning!");
}else{
out.println("Good afternoon!");
}
out.println("<hr/>");
String queryString = request.getQueryString();
out.println(queryString);
out.println("<hr/>");
String name = request.getParameter("name");
out.println(name);
out.println("<br/>");
String age = request.getParameter("age");
out.println(age);
out.println("<br/>");
String blog = request.getParameter("blog");
out.println(blog);
out.write("\r\n");
out.write(" </body>\r\n");
out.write("</html>\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);
}
}
}
? JSP声明和预定义变量
–问题
? 预定义变量(request, response, out, session, 等)是jspService方法中的局部变量。因而，由JSP声明定义的方法或辅助类中的方法都不能使用它们。怎么处理这种情况呢？
–解决方案：将它们作为参数传递，例如 <%!
private void someMethod(HttpSession s) {
doSomethingWith(s);
}
%>
<% someMethod(session); %>
–要注意：JspWriter的println方法抛出IOException异常
? 使用println的方法要使用“throws IOException”
? JSP处理的两个阶段
–JSP页面转换阶段
?页面被编译成Java类，所有的HTML标签和JSP标签被处理，来生成一个Servlet类，然而，脚本和表达式不被执行。
–请求处理阶段
?当客户端请求服务器时，处于请求处理阶段
?在该阶段脚本和表达式被执行##############################################
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