當(dāng)一個(gè)web項(xiàng)目中有多個(gè)連接器，且這些過(guò)慮器對(duì)同個(gè)url進(jìn)行過(guò)慮。這時(shí)就形成了過(guò)慮器鏈/。

在filter的配置當(dāng)中，有兩個(gè)配置:filter,filter-mapping.

Filter-mapping在前，則先執(zhí)行，在后則后執(zhí)行。

<filter>

<filter-name>first</filter-name>

<filter-class>cn.itcast.filter.FirstFilter</filter-class>

</filter>

<filter>

<filter-name>second</filter-name>

<filter-class>cn.itcast.filter.SecondFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>second</filter-name>

<url-pattern>/four</url-pattern>

</filter-mapping>

<filter-mapping>

<filter-name>first</filter-name>

<url-pattern>/four</url-pattern>

</filter-mapping>

寫一個(gè)過(guò)慮器，對(duì)所有url全部過(guò)慮，/*.在doFilter方法中，設(shè)置request的編碼為utf-8。

一般情況下，這個(gè)過(guò)慮器永遠(yuǎn)是第一個(gè)要執(zhí)行的過(guò)慮器。

最好是通過(guò)配置設(shè)置編碼。<filter><init-param>&hellip;

第一步：實(shí)現(xiàn)Filter接口，在doFIlter中接收初始化參數(shù)，設(shè)置編碼

package cn.hongxin.filter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

public class CharFilter implements Filter {

//聲明編碼的成員變量

PRivate String encoding;

public void init(FilterConfig config) throws ServletException {

encoding = config.getInitParameter("bm");

}

public void doFilter(ServletRequest request, ServletResponse response,

FilterChain chain) throws IOException, ServletException {

request.setCharacterEncoding(encoding);

//放行,必須要放行。

chain.doFilter(request, response);

}

public void destroy() {

}

}

第二步：將上面的類配置到web.xml

<filter>

<filter-name>char</filter-name>

<filter-class>cn.itcast.filter.CharFilter</filter-class>

<init-param>

<!-- 為了便于配置，在配置文件中設(shè)置編碼 -->

<param-name>bm</param-name>

<param-value>UTF-8</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>char</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

對(duì)get可以處理中文

在CharFilter中對(duì)reuqest進(jìn)行包裝。

目的：修改增強(qiáng)getParameter方法，如果是get轉(zhuǎn)碼。

第一步：聲明包裝類：

//聲明包裝類

class MyRequest extends HttpServletRequestWrapper{

public MyRequest(HttpServletRequest request) {

super(request);

}

//增強(qiáng)getParamter

@Override

public String getParameter(String name) {

String val = super.getParameter(name);

if(super.getMethod().equals("GET")){

try {

val = new String(val.getBytes("ISO-8859-1"),super.getCharacterEncoding());

} catch (UnsupportedEncodingException e) {

e.printStackTrace();

}

}

return val;

}

}

第二步：在doFilter方法中，聲明包裝類的實(shí)例

package cn.hongxin.filter;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

public class CharFilter implements Filter {

// 聲明編碼的成員變量

private String encoding;

public void init(FilterConfig config) throws ServletException {

encoding = config.getInitParameter("bm");

}

public void doFilter(ServletRequest request, ServletResponse response,

FilterChain chain) throws IOException, ServletException {

request.setCharacterEncoding(encoding);

response.setContentType("text/html;charset=" + encoding);

// 判斷是否需要包裝

HttpServletRequest req = (HttpServletRequest) request;

if (req.getMethod().equals("GET")) {

request = new MyRequest(req);

}

// 聲明包裝類的實(shí)例

// 放行

chain.doFilter(request, response);

}

public void destroy() {

}

}

// 聲明包裝類

class MyRequest extends HttpServletRequestWrapper {

public MyRequest(HttpServletRequest request) {

super(request);

}

// 增強(qiáng)getParamter

@Override

public String getParameter(String name) {

String val = super.getParameter(name);

try {

val = new String(val.getBytes("ISO-8859-1"),

super.getCharacterEncoding());

} catch (UnsupportedEncodingException e) {

e.printStackTrace();

}

return val;

}

}