FIlter(2)—案例

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案例
demo2，login.jsp请求提交到hello.jsp，该页面中有两个text，分别使用两个Filter链拦截，验证账号密码是否正确，把账号密码设置到Filter初始化参数中
login.jsp

<body>    <h3>登录</h3>    <form action="hello.jsp" method="post">        username:<input type="text" name="username" /><font color="red">${requestScope.message }</font>        <br>        password:<input type="text" name="password" /><font color="red">${requestScope.message }</font>        <br>        <input type="submit" value="Submit" />    </form></body>

hello.jsp

<body>    hello:${param.username }</body>

PasswordFilter.java

package com.test.demo2UserFilter;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;public class PasswordFilter implements Filter {    //获取到FilterConfig对象，因为要获取web应用初始化参数，必须要ServletContext()，    //而ServletContext则需要FilterConfig对象    private FilterConfig filterConfig;    @Override    public void init(FilterConfig filterConfig) throws ServletException {        this.filterConfig = filterConfig;    }    @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        //获取到初始化参数password的参数值        String initpassword = filterConfig.getServletContext().getInitParameter("password");        //获取到表单提交的参数值        String password = request.getParameter("password");        //判断账号是否正确        if(!initpassword.equals(password)){            request.setAttribute("message", "密码不正确！");            request.getRequestDispatcher("/demo2/login.jsp").forward(request, response);            return;        }        chain.doFilter(request, response);    }    @Override    public void destroy() {    }}

UsernameFilter.java

package com.test.demo2UserFilter;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;public class UsernameFilter implements Filter {    //获取初始化参数，使用init方法，为filterConfig赋值，因为init()方法可以获取到FilterConfig对象，    //而FilterConfig对象可以获取到初始化参数。    private FilterConfig filterConfig;    @Override    public void init(FilterConfig filterConfig) throws ServletException {        this.filterConfig = filterConfig;    }    @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        //获取到初始化参数username的参数值        String initUser = filterConfig.getInitParameter("username");        //获取到表单提交的参数值        String user = request.getParameter("username");        //判断账号是否正确        if(!initUser.equals(user)){            request.setAttribute("message", "用户名不正确！");            request.getRequestDispatcher("/demo2/login.jsp").forward(request, response);            return;        }        chain.doFilter(request, response);    }    @Override    public void destroy() {    }}

web.xml

  <context-param>    <param-name>password</param-name>    <param-value>1230</param-value>  </context-param>  <filter>    <filter-name>usernameFilter</filter-name>    <filter-class>com.test.demo2UserFilter.UsernameFilter</filter-class>    <init-param>      <param-name>username</param-name>      <param-value>Tom</param-value>    </init-param>  </filter>  <filter-mapping>    <filter-name>usernameFilter</filter-name>    <url-pattern>/demo2/hello.jsp</url-pattern>  </filter-mapping>  <filter>    <filter-name>passwordFilter</filter-name>    <filter-class>com.test.demo2UserFilter.PasswordFilter</filter-class>  </filter>  <filter-mapping>    <filter-name>passwordFilter</filter-name>    <url-pattern>/demo2/hello.jsp</url-pattern>  </filter-mapping>

案例
demo3，禁用浏览器缓存过滤器
cache_a.html

<body>    <a href="cache_b.html">To B Page</a></body>

cache_b.html

<body>    <a href="cache_a.html">To A Page</a>    <img alt="" src="02.jpg"></body>

cacheFilter.java

package com.test.demo3cacheFilter;import java.io.IOException;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.test.demo1Filter.HttpFilter;/** * 使用过滤器实现禁用浏览器缓存 */public class CacheFilter extends HttpFilter {    @Override    public void doFilter(HttpServletRequest req, HttpServletResponse resp,            FilterChain chain) throws IOException, ServletException {        System.out.println("cache...");        resp.setDateHeader("Expires", -1);        resp.setHeader("Cache-Control", "no-cache");        resp.setHeader("Pragme", "no-cache");        chain.doFilter(req, resp);    }}

web.xml

  <filter>    <filter-name>cacheFilter</filter-name>    <filter-class>com.test.demo3cacheFilter.CacheFilter</filter-class>  </filter>  <filter-mapping>    <filter-name>cacheFilter</filter-name>    <url-pattern>/demo3/cache_a.html</url-pattern>  </filter-mapping>

案例

demo4，编码方式过滤器
encoding1.jsp

<body>    <form action="encoding2.jsp" method="post">        name:<input type="text" name="name">        <input type="submit" value="Submit">    </form></body>

encoding2.jsp

<body>    <!-- 解决乱码方案一:使用request的setCharacterEncoding()方法，但是这样需要在每一个页面中都要写这段代码，比较麻烦-->    <%-- <%        request.setCharacterEncoding("UTF-8");    %>   --%>    <!-- 解决乱码方案二，所以过滤器就是一个不错的选择 -->    Hello:${param.name }</body>

Enconding.java

package com.test.demo4encodingFilter;import java.io.IOException;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.test.demo1Filter.HttpFilter;/** * 编码方式过滤器，通过配置参数encoding指明使用何种字符编码方式，以处理Html form请求参数的中文问题 */public class EncodingFilter extends HttpFilter {    private static final long serialVersionUID = 1L;    private String encoding;    @Override    protected void init() {        this.encoding = getFilterConfig().getServletContext().getInitParameter("encoding");    }    @Override    public void doFilter(HttpServletRequest req, HttpServletResponse resp,            FilterChain chain) throws IOException, ServletException {        req.setCharacterEncoding(encoding);        System.out.println("编码："+encoding);        chain.doFilter(req, resp);    }}

web.xml

  <filter>    <filter-name>encodingFilter</filter-name>    <filter-class>com.test.demo4encodingFilter.EncodingFilter</filter-class>  </filter>  <filter-mapping>    <filter-name>encodingFilter</filter-name>    <url-pattern>/demo4/*</url-pattern>  </filter-mapping>  <context-param>    <param-name>encoding</param-name>    <param-value>UTF-8</param-value>  </context-param>

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