自定義filter對請求及響應的編碼進行控制

首先由下圖看一下filter的原理圖

javaWeb解決中文亂碼的配置網上一大推,此處不再贅述;此處只實現自定義的filter來對request請求和response響應做相應的編碼控制,詳見下列代碼

package com.medicine.web;

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;

/**
 * 字符編碼過濾器
 * 
 * @author wk
 * 
 */
public class CharacterEncodingFilter implements Filter {

	protected String encoding = null;
	protected String resType = null;
	protected FilterConfig filterConfig = null;
	protected boolean ignore = true;

	@Override
	public void destroy() {
		// 銷燬所有全局變量的值,設爲null
		this.encoding = null;
		this.filterConfig = null;
		this.resType = null;
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain filterChain) throws IOException, ServletException {
		// 從web.xml中得到過濾器的字符串編碼
		if (ignore || (request.getCharacterEncoding() == null)) {
			if (encoding != null) {
				request.setCharacterEncoding(encoding);
				response.setCharacterEncoding(encoding);
				response.setContentType(resType);
			}

		}
		filterChain.doFilter(request, response);
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		this.encoding = filterConfig.getInitParameter("encoding");
		this.resType = filterConfig.getInitParameter("resType") == null ? "text/html; charset=utf-8"
				: filterConfig.getInitParameter("resType");
		String value = filterConfig.getInitParameter("ignore");
		if (value == null)
			this.ignore = true;
		else if (value.equalsIgnoreCase("true"))
			this.ignore = true;
		else
			this.ignore = false;
	}

}

web.xml中配置如下:

<span style="white-space:pre">	</span><filter>
   	<filter-name>CharacterEncodingFilter</filter-name>
   	<filter-class>com.medicine.web.CharacterEncodingFilter</filter-class>
   	<init-param>
   		<param-name>encoding</param-name>
   		<param-value>UTF-8</param-value>
   	</init-param>
   	<init-param>
   		<param-name>resType</param-name>
   		<param-value>text/html; charset=utf-8</param-value>
   	</init-param>
   	<init-param>
   		<param-name>ignore</param-name>
   		<param-value>true</param-value>
   	</init-param>
   </filter>
   <filter-mapping>
   		<filter-name>CharacterEncodingFilter</filter-name>
   		<url-pattern>/*</url-pattern>
   </filter-mapping>

當然其實Spring中已經爲我們提供了org.springframework.web.filter.CharacterEncodingFilter來專門解決中文亂碼的問題,但是查看它的源碼

<span style="white-space:pre">	</span>@Override
	protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		if (this.encoding != null && (this.forceEncoding || request.getCharacterEncoding() == null)) {
			request.setCharacterEncoding(this.encoding);
			if (this.forceEncoding) {
				response.setCharacterEncoding(this.encoding);
			}
		}
		filterChain.doFilter(request, response);
	}

可以發現它只對response進行了相應編碼卻沒有對響應頭進行處理,所以這也是我選擇自定義filter的原因