JSP技术实现动态页面到静态页面的方法

浏览: 122 发布日期: 2016-10-25 分类: jsp

本文是介绍了jsp技术实现动态页面到静态页面的方法,分享给大家,具体如下:

对于JSP技术实现动态页面到静态页面的方案,我们从三个步骤来说明:

JSP技术实现动态页面到静态页面的方案第一:

为了能深入浅出的理解这个框架的由来,我们首先来了解一下JSP解析器将我们写的JSP代码转换成的JAVA文件的内容。

下面是一个JSP文件test.jsp

%@ page language=java contentType=text/html;charset=GB2312 % 
% 
out.write(!--文件开始--); 
% 
html 
head 
body 
%=输出% 
/body 
/head 
/html 

经过Tomcat转换出的Java文件test$jsp.java内容如下:

package org.apache.jsp; 
import javax.servlet.*; 
import javax.servlet.http.*; 
import javax.servlet.jsp.*; 
import org.apache.jasper.runtime.*; 
 
public class test$jsp extends HttpJspBase { 
 
 static { 
 
 } 
 public testOutRedir$jsp( ) { 
 } 
 
 private static boolean _jspx_inited = false; 
 
 public final void _jspx_init() throws org.apache.jasper.runtime.JspException { 
 
  } 
  public void _jspService(HttpServletRequest request, HttpServletResponse response) 
 
    throws java.io.IOException, ServletException { 
 JspFactory _jspxFactory = null; 
 PageContext pageContext = null; 
 HttpSession session = null; 
    ServletContext application = null; 
    ServletConfig config = null; 
    JspWriter out= null; 
    Object page = this; 
    String _value = null; 
    try { 
 
      if (_jspx_inited == false) { 
        synchronized (this) { 
          if (_jspx_inited == false) { 
            _jspx_init(); 
            _jspx_inited = true; 
 
          } 
        } 
      } 
      _jspxFactory = JspFactory.getDefaultFactory(); 
 
      response.setContentType(text/html;charset=GB2312); 
 
      pageContext = _jspxFactory.getPageContext(this, request, response, 
 
             , true, 8192, true); 
 
      application = pageContext.getServletContext(); 
      config = pageContext.getServletConfig(); 
      session = pageContext.getSession(); 
      out= pageContext.getOut(); 
 
        //为了节省篇幅,我删除了解释器添加的注释 
 
        out.write(\r\n); 
 
 //上一句是由于 
 %@ page language=java contentType=text/html;charset=GB2312 %后面的换行产生的 
 
        out.write(!--文件开始--); 
 
        out.write(\r\nhtml\r\nhead\r\nbody\r\n); 
 
        out.print(输出); 
 
        out.write(\r\n/body\r\n/head\r\n/html\r\n); 
 
    } catch (Throwable t) { 
 
      if (out!= null &&out.getBufferSize() != 0) 
 
        out.clearBuffer(); 
 
      if (pageContext != null) pageContext.handlePageException(t); 
 
    } finally { 
 
      if (_jspxFactory != null) _jspxFactory.releasePageContext(pageContext); 
 
    } 
 
  } 
 
} 

 从上面的代码中可以清晰的看到JSP内建的几个对象(out、request、response、session、pageContext、application、config、page)是怎么产生的,懂servlet的朋友一看就能明白。

下面重点理解一下out对象,它被声明为JspWriter类型,JspWriter是一个抽象类,在包javax.servlet.jsp中可以找到它的定义。

abstractpublicclassjavax.servlet.jsp.JspWriterextends java.io.Writer{ 
 
   final public static intNO_BUFFER = 0; 
 
   final public static intDEFAULT_BUFFER = -1; 
 
   final public static intUNBOUNDED_BUFFER = -2; 
 
   protected intbufferSize; 
 
   protected BooleanautoFlush; 
 
   protectedjavax.servlet.jsp.JspWriter(intarg1,booleanarg2); 
 
    
 
  abstractpublicvoidnewLine()throwsIOException; 
 
  abstractpublicvoidprint(booleanarg0)throwsIOException; 
 
  abstractpublicvoidprint(chararg0)throwsIOException; 
 
  abstractpublicvoidprint(intarg0)throwsIOException; 
 
  abstractpublicvoidprint(longarg0)throwsIOException; 
 
  abstractpublicvoidprint(floatarg0)throwsIOException; 
 
  abstractpublicvoidprint(doublearg0)throwsIOException; 
 
  abstractpublicvoidprint(char[]arg0)throwsIOException; 
 
  abstractpublicvoidprint(Stringarg0)throwsIOException; 
 
  abstractpublicvoidprint(Objectarg0)throwsIOException; 
 
  abstractpublicvoidprintln()throwsIOException; 
 
  abstractpublicvoidprintln(booleanarg0)throwsIOException; 
 
  abstractpublicvoidprintln(chararg0)throwsIOException; 
 
  abstractpublicvoidprintln(intarg0)throwsIOException; 
 
  abstractpublicvoidprintln(longarg0)throwsIOException; 
 
  abstractpublicvoidprintln(floatarg0)throwsIOException; 
 
  abstractpublicvoidprintln(doublearg0)throwsIOException; 
 
  abstractpublicvoidprintln(char[]arg0)throwsIOException; 
 
  abstractpublicvoidprintln(Stringarg0)throwsIOException; 
 
  abtractpublicvoidprintln(Objectarg0)throwsIOException; 
 
  abstractpublicvoidclear()throwsIOException; 
 
  abstractpublicvoidclearBuffer()throwsIOException; 
 
  abstractpublicvoidflush()throwsIOException; 
 
  abstractpublicvoidclose()throwsIOException; 
 
  publicintgetBufferSize() ; 
 
  abstractpublicintgetRemaining(); 
 
  publicbooleanisAutoFlush(); 
 
} 

相信到这里你可能已经知道怎么做了。是的,来个偷天换日,继承JspWriter类,然后实现其定义的虚函数,然后把out变量替换成你自己实现的类的实例就ok了。

JSP技术实现动态页面到静态页面的方案第二:

实现替换

假设

%@ page language=java contentType=text/html;charset=GB2312 import=jwb.util.HtmlIntoFile,jwb.util.TempSinglet,java.io.File% 
% 
 
JspWriter outout_bak =out;String arg1=argument1;String filePath = /cache/根据参数生成文件名_ + arg1 + .html; 
 
//首先判断文件是否已经存在,如果不存在则执行本页面,否则跳转到静态页面就OK了File f = new File(pageContext.getServletContext().getRealPath(filePath)); 
 
if(f.exists()){ out_bak.clear(); pageContext.forward(filePath); System.out.println(直接转到静态页面); 
 
 return;}out= new HtmlIntoFile(pageContext.getServletContext().getRealPath(filePath));out.write(!--文件开始--); 
% 
html 
head 
body 
%= 看吧,这就是输出被重定向到文件的实现,很简单吧^_^% 
/body 
/head 
/html 
% 
out.close(); 
 
//关闭生成的静态文件out_bak.clear();pageContext.forward(filePath); 
 
System.out.println(执行本页面后再转到静态页面);return; 
% 

 JSP技术实现动态页面到静态页面的方案第三:

更新问题

下面就讨论一下如何更新生成静态文件,其实从上面实现中你可以看到,很简单的就是将生成的静态文件删除即可,至于什么时候删除,要看你的需求了。我能想到的几种情况如下:

◆当用来生成页面的数据更新时

◆如果不需要很提供时时的数据可以定时更新

◆永远不更新

那么通过这个JSP技术实现动态页面到静态页面的方案,从动态页面到静态的转变就已经告一段落,你是否有点启发呢?感谢阅读,希望能帮助到大家,谢谢大家对本站的支持!

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