【JSP開發】自己寫的過濾器Filter例子
阿新 • • 發佈：2019-02-01
目的是讓瀏覽網站的使用者所接收到的資訊的編碼方式統一為UTF-8，防止亂碼的產生
1.沒加過濾器之前:
拿Jsp工程(名叫web)中的兩個Servlet做實驗
ChineseServlet.java:
package cn.edu.hpu.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 ChineseServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String data="我的中國心"; request.setAttribute("data", data); request.getRequestDispatcher("/result").forward(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }
ResultServlet.java
package cn.edu.hpu.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 ResultServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String text=(String)request.getAttribute("data"); PrintWriter out=response.getWriter(); out.write("傳過去的那句話是（The word get is）:"+text); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }
在web.xml中配置：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <servlet> <servlet-name>ChineseServlet</servlet-name> <servlet-class>cn.edu.hpu.servlet.ChineseServlet</servlet-class> </servlet> <servlet> <servlet-name>ResultServlet</servlet-name> <servlet-class>cn.edu.hpu.servlet.ResultServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ChineseServlet</servlet-name> <url-pattern>/chin</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>ResultServlet</servlet-name> <url-pattern>/result</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
啟動伺服器，在位址列上輸入：http://localhost:8080/web/chin，得到：
?????????The word get is?:?????
出現亂碼，說明沒有指定編碼。
解決辦法：
兩邊servlet同時設定(這裡以UTF-8為編碼標準)：
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
需要顯示的時候：
String text=(String)request.getAttribute("data")+"是傳過來的那句話";
System.out.println(text);
OutputStream out =response.getOutputStream();
out.write("<html>".getBytes());
//用html技術中meta標籤模擬了一個http響應頭，來控制瀏覽器的行為
out.write("<meta http-equiv='content-type' content='text/html;charset=UTF-8'>".getBytes());
out.write(text.getBytes("UTF-8"));
out.write("</html>".getBytes());
或者直接：
response.setContentType("text/html;charset=UTF-8");
以上方法很臃腫，而且非常不簡介，無法應對多個介面，所以要使用過濾器來統一設定編碼。
2.加過濾器之後:
ChineseServlet.java:
package cn.edu.hpu.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 ChineseServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String data="我的中國心";
request.setAttribute("data", data);
request.getRequestDispatcher("/result").forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}package cn.edu.hpu.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 ResultServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String text=(String)request.getAttribute("data");
PrintWriter out=response.getWriter();
out.write("傳過去的那句話是（The word get is）:"+text);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}過濾器：
package cn.edu.hpu.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;
public class TestFilter implements Filter {
private String characterEncoding=null;
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterchain) throws IOException, ServletException {
request.setCharacterEncoding(characterEncoding);
response.setCharacterEncoding(characterEncoding);
response.setContentType("text/html;charset="+characterEncoding);
//獲取URL的路徑和引數
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String path=req.getServletPath();
String param=req.getQueryString();
if(path!=null&¶m!=null){
path=path+"?"+param;//全請求路徑
}
System.out.println("Path:"+path);
//跳轉或帶引數跳轉
request.getRequestDispatcher(path).forward(request, response);
}
public void init(FilterConfig filterConfig) throws ServletException {
characterEncoding = filterConfig.getInitParameter("characterEncoding");
}
}在web.xml中配置：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<filter>
<filter-name>TestFilter</filter-name>
<filter-class>cn.edu.hpu.filter.TestFilter</filter-class>
<init-param>
<param-name>characterEncoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>TestFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>ChineseServlet</servlet-name>
<servlet-class>cn.edu.hpu.servlet.ChineseServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>ResultServlet</servlet-name>
<servlet-class>cn.edu.hpu.servlet.ResultServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ChineseServlet</servlet-name>
<url-pattern>/chin</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ResultServlet</servlet-name>
<url-pattern>/result</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>啟動伺服器，在位址列上輸入：http://localhost:8080/web/chin，得到：
傳過去的那句話是（The word get is）:我的中國心
沒有發生亂碼，說明過濾成功！！