案例四：解决全网站的post和get方式乱码

首先，我们来回顾下，当我们打开浏览器访问服务器的时候如果传送过去一些数据，如果发过去的数据有中文，我们不可避免的都要解决乱码（不管其是get请求还是post请求。）

类似的我们总要调用如下的代码：

Get请求时：

String username = request.getParameter(“username”);

new String(username.getBytes(“ISO8859-1”),”UTF-8”);

Post请求时：

request.setCharacterEncoding(“UTF-8”);

由于我们的过滤器是在执行servlet之前执行的，然后调用filterChain.doFilter(request,response) 方法才放行，那么我们就可以在配置一个过滤器，这个过滤器对任何请求都拦截，那么在拦截的时候就对request的编码进行处理，然后再放行，就可以解决所有的乱码问题了。

使用Decorator模式包装request对象，完全解决get、post请求方式下的乱码问题。

1.创建处理get/post请求参数乱码问题的MyHttpServletRequestWrapper

package blog.csdn.net.web.filter;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/**
 * HttpServletRequest增强类
 * 
 * @author mChenys
 *
 */
public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {
	private HttpServletRequest request;

	public MyHttpServletRequestWrapper(HttpServletRequest request) {
		super(request);
		this.request = request;
	}

	@Override
	public String getParameter(String name) {
		String[] values = this.getParameterValues(name);
		return values == null ? null : values[0];
	}

	@Override
	public String[] getParameterValues(String name) {
		Map<String, String[]> map = this.getParameterMap();
		String[] values = map.get(name);
		return values;
	}

	private boolean hasEncode;// 避免重复编码

	/**
	 * 上面2个方法最终是调用这个方法,所有统一在这个方法处理请求参数乱码问题
	 */
	@Override
	public Map<String, String[]> getParameterMap() {
		Map<String, String[]> map = super.getParameterMap();
		String method = this.request.getMethod();
		try {
			if (method.equalsIgnoreCase("post")) {
				// post请求,直接设置这句话即可
				this.request.setCharacterEncoding("utf-8");
			} else if (method.equalsIgnoreCase("get")) {
				// 通过遍历参数名获取说有的参数值
				if (!hasEncode) {
					hasEncode = true;
					for (String name : map.keySet()) {
						String[] values = map.get(name);
						for (int i = 0; i < values.length; i++) {
							// 在这里处理编码
							values[i] = new String(values[i].getBytes("iso8859-1"), "utf-8").trim();
						}
					}
				}
			}
		} catch (Exception e) {
		}
		return map;
	}
}

2.创建GenericEncodingFilter

package blog.csdn.net.web.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 处理全站乱码问题的filter
 * @author mChenys
 *
 */
public class GenericEncodingFilter implements Filter{

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		
		//强转
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		
		//统一处理响应编码
		httpServletResponse.setCharacterEncoding("utf-8");
		
		//统一处理请求参数编码,使用增强后的request包装httpServletRequest
		MyHttpServletRequestWrapper req  = new MyHttpServletRequestWrapper(httpServletRequest);
		
		//放行
		chain.doFilter(req, httpServletResponse);
		
		
	}

	@Override
	public void destroy() {
		
	}

}

 3.注册filter

<!--  全站乱码处理-->
	<filter>
		<filter-name>GenericEncodingFilter</filter-name>
		<filter-class>blog.csdn.net.web.filter.GenericEncodingFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>GenericEncodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>