Java filter中的chain.doFilter使用詳解

第Javafilter中的chain.doFilter使用詳解目錄filter中的chain.doFilter使用chain.doFilter作用舉例說(shuō)明Filter中chain.doFilter(req,res)的理解用法

filter中的chain.doFilter使用

chain.doFilter作用

1.一般filter都是一個(gè)鏈,web.xml里面配置了幾個(gè)就有幾個(gè)。一個(gè)一個(gè)的連在一起

request-filter1-filter2-filter3-….-requestresource.

2.chain.doFilter將請(qǐng)求轉(zhuǎn)發(fā)給過(guò)濾器鏈下一個(gè)filter,如果沒(méi)有filter那就是你請(qǐng)求的資源

舉例說(shuō)明

1.input.jsp是用來(lái)提交輸入的:當(dāng)提交后，過(guò)濾器檢測(cè)姓名和年齡.

2.如果正常的話會(huì)提交給output.jsp如果不正常提交給erroroutput.jsp.

3.在此,同時(shí)也有一個(gè)過(guò)濾器，防止亂碼問(wèn)題存在,該過(guò)濾器檢測(cè)一個(gè)頁(yè)面是否設(shè)置了字符編碼，如果沒(méi)有則進(jìn)行設(shè)置。

1.input.jsp

formaction="output.jsp"name="form"method="post"

table

tdname/td

tdinputtype="text"name="name"http://td

/tr

tdage/td

tdinputtype="text"name="age"http://td

/tr

tdinputtype="submit"name="ok"value="ok"http://td

/tr

/table

/form

2.web.xml

filter

description/description

display-nameencodefilter/display-name

filter-nameencodefilter/filter-name

filter-classservletbean.encodefilter/filter-class

init-param

param-nameencoding/param-name

param-valueGB2312/param-value

/init-param

/filter

filter-mapping

filter-nameencodefilter/filter-name

url-pattern/*/url-pattern

/filter-mapping

filter

description/description

display-namemyfilter/display-name

filter-namemyfilter/filter-name

filter-classservletbean.myfilter/filter-class

/filter

filter-mapping

filter-namemyfilter/filter-name

url-pattern/output.jsp/url-pattern

/filter-mapping

3.encodefilter.java

packageservletbean;

publicclassencodefilterimplementsFilter{

publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainchain)throwsIOException,ServletException{

if(request.getCharacterEncoding()==null){

System.out.println(encoding);

request.setCharacterEncoding(encoding);

chain.doFilter(request,response);//到下一個(gè)鏈

publicvoidinit(FilterConfigfConfig)throwsServletException{

this.config=fConfig;

encoding=fConfig.getInitParameter("encoding");//獲得目標(biāo)編碼格式

}

3.myfilter.java

packageservletbean;

importjavax.swing.JOptionPane;

publicclassmyfilterimplementsFilter{

publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainchain)throwsIOException,ServletException{

response.setContentType("text/html");

response.setCharacterEncoding("GB2312");

PrintWriterout=response.getWriter();

Stringname="";

Stringage="";

intage1;

name=request.getParameter("name");

age=request.getParameter("age");

RequestDispatcherdispatch=request.getRequestDispatcher("erroroutput.jsp");

if(name==null||name==""||name==""||age==null){

JOptionPane.showMessageDialog(null,"用戶名和年齡輸入錯(cuò)誤！");

dispatch.forward(request,response);

return;

else{

try{

age1=Integer.parseInt(age);

}catch(Exceptione){

//JOptionPane.showMessageDialog(null,"年齡必須為數(shù)字！");

dispatch.forward(request,response);

return;//如果是錯(cuò)誤頁(yè)面就到erroroutput.jsp中

//這里表示是正確的，也就是說(shuō)，他回去找下一個(gè)鏈，但是它下面已經(jīng)沒(méi)有了，所以就會(huì)去跳轉(zhuǎn)頁(yè)面了，此跳轉(zhuǎn)的頁(yè)面就是action="output.jsp"了

chain.doFilter(request,response);

Filter中chain.doFilter(req,res)的理解

在寫(xiě)代碼中，每次看到Filter(過(guò)濾器)中chain.doFilter(req,res)；都不懂為什么要加這一句，他的作用是什么；

代碼下面也有：

@Override

publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainchain)throwsIOException,ServletException{

ContentCachingRequestWrapperreq=newContentCachingRequestWrapper((HttpServletRequest)request);

ContentCachingResponseWrapperres=newContentCachingResponseWrapper((HttpServletResponse)response);

longstartTime=System.currentTimeMillis();

StringserverUrl=req.getServletPath();

//不懂這句什么意思

chain.doFilter(req,res);

longendTime=System.currentTimeMillis();

try{

intstatus=res.getStatus();

Stringcharset=res.getCharacterEncoding();

//響應(yīng)體

StringresponsePayload=getPayLoad(res.getContentAsByteArray(),res.getCharacterEncoding());

res.copyBodyToResponse();

if(writeLogService==null){

writeLogService=(WriteLogService)ServiceLocator.getInstance().getCtx().getBean("writeLogServiceImpl");

writeLogService.writeLog(startTime,endTime,serverUrl,postparams,status,responsePayload,charset);

}catch(Exceptione){

e.printStackTrace();

}

用法