Java-Filter过滤器用于过滤整个项目的编码

整个分为实现类以及在web.xml文件中对编写的filter类进行注册

package cn.itcast.itcaststore.web.filter;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;
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;
/**
 * 编码过滤器（用于统一项目编码）
 */
public class EncodingFilter implements Filter {
	public void init(FilterConfig filterConfig) throws ServletException {

	}
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// 处理请求乱码
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletRequest myRequest = new MyRequest(httpServletRequest);
		// 处理响应乱码
		response.setContentType("text/html;charset=utf-8");
		chain.doFilter(myRequest, response);
	}
	public void destroy() {

	}
}
// 自定义request对象
class MyRequest extends HttpServletRequestWrapper {
	private HttpServletRequest request;
	private boolean hasEncode;
	public MyRequest(HttpServletRequest request) {
		super(request);// super必须写
		this.request = request;
	}
	// 对需要增强方法 进行覆盖
	@SuppressWarnings({ "unchecked", "rawtypes" })
	@Override
	public Map getParameterMap() {
		// 先获得请求方式
		String method = request.getMethod();
		if (method.equalsIgnoreCase("post")) {
			// post请求
			try {
				// 处理post乱码
				request.setCharacterEncoding("utf-8");
				return request.getParameterMap();
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}
		} else if (method.equalsIgnoreCase("get")) {
			// get请求
			Map parameterMap = request.getParameterMap();
			if (!hasEncode) { // 确保get手动编码逻辑只运行一次
				for (String parameterName : parameterMap.keySet()) {
					String[] values = parameterMap.get(parameterName);
					if (values != null) {
						for (int i = 0; i < values.length; i++) {
							try {
							      values[i] = new String(values[i].getBytes("ISO-8859-1"),"utf-8");
							    } catch (UnsupportedEncodingException e) {
								    e.printStackTrace();
							}
						}
					}
				}
				hasEncode = true;
			}
			return parameterMap;
		}
		return super.getParameterMap();
	}
	@Override
	public String getParameter(String name) {
		@SuppressWarnings("unchecked")
		Map parameterMap = getParameterMap();
		String[] values = parameterMap.get(name);
		if (values == null) {
			return null;
		}
		return values[0]; // 取回参数的第一个值
	}
	@Override
	public String[] getParameterValues(String name) {
		@SuppressWarnings("unchecked")
		Map parameterMap = getParameterMap();
		String[] values = parameterMap.get(name);
		return values;
	}
}

web.xml配置

<filter>

<filter-name>encodingFilter</filter-name>

<filter-class>cn.itcast.itcaststore.web.filter.EncodingFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>encodingFilter</filter-name>

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

</filter-mapping>