servlet技巧abc
1.利用stringbuffer提高速度.
servlets经常需要显示html标记,我们很自然想到println()和string串联起来,
但是string是很慢的,但是我们用stringbuffer它快很多.
比较这两例:
用string,
for (int i=0; i<100; i++) {
out.println("data for " + i + " is " + method1() + " , " + method2() + ".<br>");
}
out.close();
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用stringbuffer,可发这样:
stringbuffer buf = new stringbuffer();
for (int i=0; i<100; i++) {
buf.append("data for ").append(i).append(" is ").append(method1());
buf.append(" , ").append(method2()).append(".<br>");
}
response.setcontentlength(buf.length());
out.println(buf.tostring());
out.close();
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我们用stringbuffer实现我个问题减少了对像的创建个数,
所以它比out.println()更有效.
2.利用http status codes显示出错信息.
比如我们常用类似下面的处理
public void openfile( string filename ) {
try {
someothermethodtoopenafile( filename );
} catch( filenotfoundexception e ) {
out.println( "sorry... file not found." );
}
}
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为了得用status codes,我们可以这样得用http出错信息:
/* 'response' variable is an object of the
httpservletresponse class.
*/
public void openfile( string filename ) {
try {
someothermethodtoopenafile( filename );
} catch( filenotfoundexception e ) {
response.senderror( response.sc_not_found );
}
}
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3.在frame调用servlet动态生成页面.
在静态页内包含frame,使"src"指向你希望的servlet,如:
<frameset rows="20%,*" cols="80%,*">
<frame name="frame1" src="/servlet/someservlet">
<frame name="frame2" src="/servlet/anotherservlet">
</frameset>
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frame的src属性可以指向静态页或是servlet.
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