第六章 JSP的上机练习

• 编写第一个jsp文件
• JSP基本语法

在WebRoot下新建一个HelloWord.jsp

  
    Welcome to yj's JSP 

  

然后找到workplace文件夹有

在C:UsersAdministratorWorkspacesMyEclipse Professional 2014.metadata.me_tcatworkCatalinalocalhostChapter06orgapachejsp文件夹下可以找到
可以看出JSP文件被转换成了.java,.class文件

打开java文件可以看到源代码

package org.apache.jsp;

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

public final class HelloWorld_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("rn");
      out.write("rn");
      out.write("rn");
      out.write("rn");
      out.write("  rn");
      out.write("    rn");
      out.write("    rn");
      out.write("    rn");
      out.write("    rn");
      out.write("trn");
      out.write("trn");
      out.write("t    rn");
      out.write("trn");
      out.write("trn");
      out.write("trn");
      out.write("rn");
      out.write("  rn");
      out.write("  rn");
      out.write("  rn");
      out.write("    Welcome to yj's JSP 
rn");
      out.write("  rn");
      out.write("rn");
    } 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);
    }
  }
}

在head里面使用<%! %>声明变量，定义了两个变量a,b以及print（）方法,在body里面运行使用了<% %>输出了两个常量的乘积，以及print（）方法中的返回信息。
代码为：

	 
	<%!int a=3,b=2; %>
	<%!public String print(){
	   String str="you are the lucky girl!";
	   return str;}
	 %>

  
  
  
    <% out.println(a*b);%>
    

    <%out.println(print()); %>
  

再来一个例子：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


<%
    int i=0;
    out.print(i+"号");
%>


<%=i+1
%>


<%!
    public class Student
    {
        int age;
        String name;

        public Student(String name,int age) {
            this.age = age;
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return "Student{" + "age=" + age + ", name='" + name + ''' + '}';
        }
    }
%>

<%
    Student girl = new Student("踌躇樱桃", 8);
    out.println(girl.toString());
%>
<%--注释一下 --%>

在注释的时候，页面中不显示

可以再查看源代码中查看

可以看出jsp的注释信息没有显示，因为在tomcat编译jsp文件时，注释会被忽略掉。但是对于html的注释会认为是内容传送到网页上。