用Filter为Servlet统一做中文编码处理

每当我们在Servlet中传递中文参数的时候总是会碰到乱码的问题，而通常的解决方式是在request请求进行解码处理，然后在response响应做编码处理：

request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");

但是当业务复杂时，在Servlet中重复书写解码和编码的代码会十分繁琐，让代码看起来很臃肿。其实，可以通过Filter过滤器进行统一的解码编码处理。

一个简易的显示本地时间的小例子

FirstServlet.java代码:

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class FirstServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        Date date = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        String dateString = formatter.format(date);
        String data=dateString;

        request.setAttribute("data", data);
        request.getRequestDispatcher("/show").forward(request, response);
    }

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        doPost(request,response);
    }
}

ShowServlet.java代码:

import java.io.IOException;
import java.io.PrintWriter;

public class ShowServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        // 设置刷新自动加载的事件间隔为 3 秒
        response.setIntHeader("Refresh", 3);

        String text=(String)request.getAttribute("data");
        PrintWriter out=response.getWriter();

        out.write("本地时间（The time is）:"+text+"（3秒后自动刷新）");
}

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        doPost(request,response);
    }
}

DemoFilter.java代码:

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;

public class DemoFilter implements javax.servlet.Filter {
    public void destroy() {
    }

    public void doFilter(javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain chain) throws javax.servlet.ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        //获取URL的路径和参数
        HttpServletRequest req = (HttpServletRequest) request;
        String path=req.getServletPath();
        String param=req.getQueryString();
        if(path!=null&&param!=null){
            path=path+"?"+param;//全请求路径
        }
        System.out.println("Path:"+path);
        //跳转或带参数跳转
        request.getRequestDispatcher(path).forward(request, response);
    }

    public void init(javax.servlet.FilterConfig config) throws javax.servlet.ServletException {

    }

}

web.xml配置文件:

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <filter>
        <filter-name>DemoFilter</filter-name>
        <filter-class>com.sunsharing.DemoFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>DemoFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <servlet>
        <servlet-name>FirstServlet</servlet-name>
        <servlet-class>com.sunsharing.FirstServlet</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ShowServlet</servlet-name>
        <servlet-class>com.sunsharing.ShowServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FirstServlet</servlet-name>
        <url-pattern>/first</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ShowServlet</servlet-name>
        <url-pattern>/show</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

完毕后启动tomcat，在浏览器的url地址输入：localhost:8080/first

预览效果：