本文實(shí)例講述了jsp實(shí)現(xiàn)將動(dòng)態(tài)網(wǎng)頁轉(zhuǎn)換成靜態(tài)頁面的方法。分享給大家供大家參考。具體如下：
如果我可以將jsp動(dòng)態(tài)網(wǎng)頁轉(zhuǎn)換成靜態(tài)頁面，那么訪問的時(shí)候就不需要頻繁的訪問數(shù)據(jù)庫(kù)了。
jsp 顯示內(nèi)容緩存技巧
前段時(shí)間做自己社區(qū)的論壇，在jive 的基礎(chǔ)上做一個(gè)頁面顯示所有論壇的帖子,可以稱之為總版，模仿forum 類的接口做個(gè)superforum 并且實(shí)現(xiàn)cachable，不過因?yàn)檫@個(gè)頁面刷新量比較大，雖然被cache 了，我還是想辦法進(jìn)行頁面的緩存，感覺用jsp 產(chǎn)生的html靜態(tài)內(nèi)容當(dāng)緩存,頁面訪問速度應(yīng)該有所提高。
首先想到的一種辦法,是采用java.net 的urlconnection 把服務(wù)器上的jsp 抓過來做緩存,不過我覺得這樣做太見外了,自己服務(wù)器上的東西,為何要用http 去訪問.于是想另外一個(gè)辦法，把jsp 的out 對(duì)象的輸出控制到自己希望的地方.比如輸出到靜態(tài)文件,又或者保存成全局的字符串變量.這樣的話,瀏覽就不需要執(zhí)行jsp,只是瀏覽該html 了.僅僅在數(shù)據(jù)有更新的時(shí)候進(jìn)行一次update 操作,把jsp 重新輸出為html.
我覺得，瀏覽事件比數(shù)據(jù)插入或更新發(fā)生的次數(shù)多的時(shí)候.不妨試試這個(gè)辦法來提高頁面訪問速度.
整件事情有點(diǎn)像把jsp 當(dāng)作模板,生成靜態(tài)的html 頁面.
將如下代碼寫入web-xml：
filter>
filter-name>filecapturefilter/filter-name>
filter-class>com.junjing.filter.filecapturefilter/filter-class>
/filter>
filter-mapping>
filter-name>filecapturefilter/filter-name>
url-pattern>/latest.jsp/url-pattern>
/filter-mapping>
latest.jsp 是我要cache 的頁面
java 源碼代碼如下：
/** * start file filecapturefilter.java */
package com.junjing.filter;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class filecapturefilter implements filter
{
private string protdirpath;
public void init(filterconfig filterconfig)
throws servletexception
{
protdirpath = filterconfig.getservletcontext().getrealpath("/");
}
public void dofilter(servletrequest request,servletresponse response,filterchain
chain)
throws ioexception, servletexception
{
string filename = protdirpath + "forum/lastest.html";
printwriter out = response.getwriter();
filecaptureresponsewrapper responsewrapper = new
filecaptureresponsewrapper((httpservletresponse)response);
chain.dofilter(request, responsewrapper);
// fill responsewrapper up
string html = responsewrapper.tostring();
//得到的html 頁面結(jié)果字符串
// responsewrapper.writefile(filename);
// dump the contents 寫成html 文件，也可以保存在內(nèi)存
//responsewrapper.writeresponse( out );
// back to browser
//responsewrapper.sendredirect("lastestthread.jsp");
}
public void destroy() {}
}
/** * end file filecapturefilter.java */
/** * start file filecaptureresponsewrapper.java */
package com.junjing.filter;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class filecaptureresponsewrapper
extends httpservletresponsewrapper
{
private chararraywriter output;
public string tostring()
{
return output.tostring();
}
public filecaptureresponsewrapper(httpservletresponse response)
{
super(response);
output = new chararraywriter();
}
public printwriter getwriter()
{
return new printwriter(output);
}
public void writefile(string filename)
throws ioexception
{
filewriter fw = new filewriter(filename);
fw.write( output.tochararray() );
fw.close();
}
public void writeresponse(printwriter out)
{
out.print( output.tochararray() );
}
}
/** * end file filecaptureresponsewrapper.java */
附件源代碼：
不過采用resin 服務(wù)器的話，以上代碼會(huì)失效。因?yàn)閞esin 沒有實(shí)現(xiàn)getwriter 方法，而是采用getoutputstream 取而代之，所以必須修改些代碼來迎合resin 運(yùn)行環(huán)境：
/** * start file filecaptureresponsewrapper.java */
package com.junjing.filter;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class filecaptureresponsewrapper
extends httpservletresponsewrapper
{
private chararraywriter output;
public string tostring()
{
return output.tostring();
}
public filecaptureresponsewrapper(httpservletresponse response)
{
super(response);
output = new chararraywriter();
}
public printwriter getwriter()
{
return new printwriter(output);
}
public void writefile(string filename)
throws ioexception
{
filewriter fw = new filewriter(filename);
fw.write( output.tostring());
fw.close();
}
public servletoutputstream getoutputstream()
throws java.io.ioexception
{
return new servletoutputstream();
}
public void write(int b)
throws ioexception
{
output.write(b);
}
public void write(byte b[])
throws ioexception
{
output.write(new string(b,"gbk"));
}
public void write(byte b[], int off, int len)
throws ioexception
{
output.write(new string(b, off, len));
}
};
}
public void writeresponse(printwriter out)
{
out.print(output.tochararray());
}
}
/** * end file filecaptureresponsewrapper.java */
希望本文所述對(duì)大家的JSP程序設(shè)計(jì)有所幫助。
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