java利用过滤器实现编码的转换,内容输出的替换

2023-03-09 07:50:24

在页面建个表单

 <form action="login.do" method="post">

        <input type="text" name="username" />

        <input type="submit" value="确定" />

    </form>

建个servlet

web.xml

  <servlet>

    <servlet-name>LoginServlert</servlet-name>

    <servlet-class>servlet.LoginServlert</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>LoginServlert</servlet-name>

    <url-pattern>/login.do</url-pattern>

  </servlet-mapping>
package servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LoginServlert extends HttpServlet {

    public LoginServlert() {

        super();

    }

    public void destroy() {

        super.destroy();

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String username = request.getParameter("username");

        System.out.println("获取的username:>>>>>>"+username);

    }

    public void init() throws ServletException {

    }

}

java利用过滤器实现编码的转换,内容输出的替换

后台情况是这样的:

java利用过滤器实现编码的转换,内容输出的替换

乱码了.

可以通过过滤器来解决

新建一个过滤器EncodingFilter.java

package 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;

public class EncodingFilter implements Filter{

    private String encoding = "";

    private String filterName = "";

    public void init(FilterConfig filterConfig) throws ServletException {

        encoding = filterConfig.getInitParameter("encoding");

        filterName = filterConfig.getFilterName();

        if (encoding == null || "".equals(encoding)) {

            encoding = "UTF-8";

        }

        System.out.println("获得编码值......");

    }

    public void doFilter(ServletRequest request, ServletResponse res,

            FilterChain chain) throws IOException, ServletException {

        HttpServletRequest req=(HttpServletRequest)request;

        System.out.println("请求被" + filterName + "过滤了.......");

        // 分别对请求和响应进行编码设置

        request.setCharacterEncoding(encoding);

        res.setCharacterEncoding(encoding);

        chain.doFilter(req, res);

        System.out.println("响应被被" + filterName + "过滤了.......");

    }

    public void destroy() {

        System.out.println("请求被销毁......");

    }

}

在web.xml中配置filter

   <filter>

      <filter-name>EncodingFilter</filter-name>

      <filter-class>filter.EncodingFilter</filter-class>

      <init-param>

          <param-name>encoding</param-name>

          <param-value>utf-8</param-value>

      </init-param>

  </filter>

  <filter-mapping>

      <filter-name>EncodingFilter</filter-name>

      <url-pattern>*.do</url-pattern>

  </filter-mapping>

跑起来:

java利用过滤器实现编码的转换,内容输出的替换

正常了.

我们换在地址栏里输入汉字,看看是否乱码.

java利用过滤器实现编码的转换,内容输出的替换

结果是这样的

java利用过滤器实现编码的转换,内容输出的替换

过滤器不起作用了,怎么办.

其实request.setCharacterEncoding(encoding);只对消息体中的数据起作用,对url中的参数不起作用了.

对上面的过滤器进行优化.

编写RequestEncodingWrapper.java

package filter;

import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

public class RequestEncodingWrapper extends HttpServletRequestWrapper {

    private String encoding = "";

    public RequestEncodingWrapper(HttpServletRequest request) {

        // 必须调用父类构造方法

        super(request);

    }

    public RequestEncodingWrapper(HttpServletRequest request,String encoding){

        // 必须调用父类构造方法

        super(request);

        this.encoding=encoding;

    }

    @Override

    public String getParameter(String name) {

        String value=getRequest().getParameter(name);

        try {

            //将参数值进行编码转换

            if(value!=null&&!"".equals(value)){

                value=new String(value.trim().getBytes("iso-8859-1"),encoding);

            }

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        }

        return value;

    }

}

优化EncodingFilter.java后

package 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;

public class EncodingFilter implements Filter {

    private String encoding = "";

    private String filterName = "";

    public void init(FilterConfig filterConfig) throws ServletException {

        encoding = filterConfig.getInitParameter("encoding");

        filterName = filterConfig.getFilterName();

        if (encoding == null || "".equals(encoding)) {

            encoding = "UTF-8";

        }

        System.out.println("获得编码值......");

    }

    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        HttpServletRequest req=(HttpServletRequest)request;

        System.out.println("请求被" + filterName + "过滤了.......");

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

            req=new RequestEncodingWrapper(req,encoding);

        }else {

            request.setCharacterEncoding(encoding);

        }

        // 分别对请求和响应进行编码设置

        response.setCharacterEncoding(encoding);

        chain.doFilter(req, response);

        System.out.println("响应被被" + filterName + "过滤了.......");

    }

    public void destroy() {

        System.out.println("请求被销毁......");

    }

}

java利用过滤器实现编码的转换,内容输出的替换

好了.

Filter接口有三个方法:

init(FilterConfig filterConfig) 初始化过滤器,filterConfig参数可以得到过滤器初始化的配置参数信息.

doFilter(ServletRequest request, ServletResponse res,FilterChain chain)

request表示客户端的请求,rewponse表示对应请求的响应,chain是过滤器对象,.在该方法中的特定过滤器完成后,

可调用doFilter请求传给过滤器中的下一个过滤器,也可以直接返回响应内容,还可以将目标重定向.

destroy():释放过滤器中使用的资源.

参数FilterConfig filterConfig有四个方法:

public String getFilterName()　　　　得到过滤器的名字

public String getInitParameter(String name)　　　　得到过滤器中初始化的参数值.

publi Enumeration getInitParameterNames()　　　　得到过滤器配置中的所有初始化参数名字的枚举类型.

publi ServletContext getServlet()　　　　得到Servlet上下文对象.

说完了请求,我们再来说说响应.

我们经常需要在向浏览器输出内容时,过滤一些敏感词汇.

新建一个内容替换的封装器ResponseReplaeWrapper.java

package filter;

import java.io.CharArrayWriter;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpServletResponseWrapper;

public class ResponseReplaeWrapper extends HttpServletResponseWrapper {

    private CharArrayWriter charWriter = new CharArrayWriter();

    public ResponseReplaeWrapper(HttpServletResponse response){

        //必须调用父类构造方法

        super(response);

    }

    public PrintWriter getWriter() throws IOException{

        //返回字符数组Writer,缓存内容

        return new PrintWriter(charWriter);

    }

    public CharArrayWriter getCharWriter(){

        return charWriter;

    }

}

过滤器:

package filter;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Properties;

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.HttpServletResponse;

public class ReplaceFilter implements Filter {

    private Properties propert = new Properties();

    public void init(FilterConfig filterConfig) throws ServletException {

        System.out.println("ReplaceFilter  init.....");

        // 通过filterConfig获得初始胡文件名

        String filePath = filterConfig.getInitParameter("filePath");

        try {

            // 导入资源文件

            propert.load(ReplaceFilter.class.getClassLoader()

                    .getResourceAsStream(filePath));

        } catch (FileNotFoundException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        HttpServletResponse res = (HttpServletResponse) response;

        // 实例化响应器包装类

        ResponseReplaeWrapper resp = new ResponseReplaeWrapper(res);

        chain.doFilter(request, resp);

        // 缓存输出字符

        String outString = resp.getCharWriter().toString();

        // 循环替换不合法的字符

        for (Object o : propert.keySet()) {

            String key = (String) o;

            outString = outString.replace(key, propert.getProperty(key));

        }

        // 利用原先的HttpServletResponse输出字符

        PrintWriter out = res.getWriter();

        out.write(outString);

    }

    public void destroy() {

        System.out.println("ReplaceFilter destroy......");

    }

}

在web.xml中配置过滤器

<filter>

      <filter-name>ReplaceFilter</filter-name>

      <filter-class>filter.ReplaceFilter</filter-class>

      <init-param>

          <param-name>filePath</param-name>

          <param-value>/replace_ZH.properties</param-value>

      </init-param>

  </filter>

  <filter-mapping>

      <filter-name>ReplaceFilter</filter-name>

      <url-pattern>*.do</url-pattern>

  </filter-mapping>

在src下新建配置文件replace_ZH.properties

java利用过滤器实现编码的转换,内容输出的替换

建个测试的servlet

package servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ResponseServlet extends HttpServlet {

    public ResponseServlet() {

        super();

    }

    public void destroy() {

        super.destroy(); // Just puts "destroy" string in log

        // Put your code here

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html");

        PrintWriter out = response.getWriter();

        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");

        out.println("<HTML>");

        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");

        out.println("  <BODY>");

        out.println("思思博士<br/>色情<br/>赌博<br/>dfdffddf");

        /*out.print("    This is ");

        out.print(this.getClass());

        out.println(", using the GET method");*/

        out.println("  </BODY>");

        out.println("</HTML>");

        out.flush();

        out.close();

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html");

        PrintWriter out = response.getWriter();

        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");

        out.println("<HTML>");

        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");

        out.println("  <BODY>");

        out.print("    This is ");

        out.print(this.getClass());

        out.println(", using the POST method");

        out.println("  </BODY>");

        out.println("</HTML>");

        out.flush();

        out.close();

    }

    public void init() throws ServletException {

    }

}

java利用过滤器实现编码的转换,内容输出的替换

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