Servlet 3.0 HTTP 404 - 请求的资源()不可用

时间:2012-11-17 13:24:38

标签: tomcat servlets annotations tomcat7 servlet-3.0

环境:

  • Ubuntu 12.04
  • Apache Tomcat 7.0.27
  • Eclipse 4.2(Juno)
  • Servlet 3.0
  • Openjdk 7

尝试使用Servlet 3.0执行FileCounter,我在URL

上收到此错误

的http://本地主机:8080 / wtp.filecounter /

不一定是 http:// localhost:8080 / wtp.filecounter / FileCounter

  

Estado HTTP 404 -

     

输入 Informe de estado

     

mensaje

     

descripción El recurso requerido()noestádisponible。

     

Apache Tomcat / 7.0.26

结构

wtp.filecounter
   dao
      FileDao.java
   servlets
      FileCounter.java

FileDao.java 读取并更新文件的访问者

package wtp.filecounter.dao;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

public class FileDao {

  public int getCount() {
    int count = 0;
    // Load the file with the counter
    FileReader fileReader = null;
    BufferedReader bufferedReader = null;
    PrintWriter writer = null ; 
    try {
      File f = new File("FileCounter.initial");
      if (!f.exists()) {
        f.createNewFile();
        writer = new PrintWriter(new FileWriter(f));
        writer.println(0);
      }
      if (writer !=null){
        writer.close();
      }

      fileReader = new FileReader(f);
      bufferedReader = new BufferedReader(fileReader);
      String initial = bufferedReader.readLine();
      count = Integer.parseInt(initial);
    } catch (Exception ex) {
      if (writer !=null){
        writer.close();
      }
    }
    if (bufferedReader != null) {
      try {
        bufferedReader.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    return count;
  }

  public void save(int count) throws Exception {
    FileWriter fileWriter = null;
    PrintWriter printWriter = null;
    fileWriter = new FileWriter("FileCounter.initial");
    printWriter = new PrintWriter(fileWriter);
    printWriter.println(count);

    // Make sure to close the file
    if (printWriter != null) {
      printWriter.close();
    }
  }
} 

FileCounter.java 用于读取计数器并以纯文本格式写入的servlet

package wtp.filecounter.servlets;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import wtp.filecounter.dao.FileDao;

/**
 * Servlet implementation class FileCounter
 */
@WebServlet("/FileCounter")
public class FileCounter extends HttpServlet {
  private static final long serialVersionUID = 1L;

  int count;
  private FileDao dao;

  public void init() throws ServletException {
    dao = new FileDao();
    try {
      count = dao.getCount();
    } catch (Exception e) {
      getServletContext().log("An exception occurred in FileCounter", e);
      throw new ServletException("An exception occurred in FileCounter"
          + e.getMessage());
    }
  }

  protected void doGet(HttpServletRequest request,
      HttpServletResponse response) throws ServletException, IOException {
    // Set a cookie for the user, so that the counter does not increate
    // everytime the user press refresh
    HttpSession session = request.getSession(true);
    // Set the session valid for 5 secs
    session.setMaxInactiveInterval(5);
    response.setContentType("text/plain");
    PrintWriter out = response.getWriter();
    if (session.isNew()) {
      count++;
    }
    out.println("This site has been accessed " + count + " times.");
  }

  public void destroy() {
    super.destroy();
    try {
      dao.save(count);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
  <display-name>wtp.filecounter</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

对于什么是错的任何想法?

当我在服务器上运行时,项目打开''http:// localhost:8080 / wtp.filecounter /''而不是''http:// localhost:8080 / wtp .filecounter / FileCounter'',第二个URL工作

5 个答案:

答案 0 :(得分:0)

您的servlet映射到/FileCounter(这是@WebServlet("/FileCounter")注释的作用)。它是webapp的一部分,部署在某个上下文路径下(假设上下文路径为/myFirstWebApp)。因此,调用servlet的URL是:

http://localhost:8080/myFirstWebApp/FileCounter

答案 1 :(得分:0)

您的应用程序的名称是wtp.filecounter,并且您有一个带有映射"/FileCounder"的servlet。这就是为什么如果你击中 在浏览器中"http://localhost:8080/wtp.filecounter/FileCounter"调用了带有映射doGet的servlet的"/FileCounter"方法,您就会得到响应。

答案 2 :(得分:0)

'http:// localhost:8080 / wtp.filecounter / FileCounter'的工作原理是因为在那里找到了servlet。

“wtp.filecounter”部分是您的应用程序上下文。如果要使用“http:// localhost:8080 / wtp.filecounter /”访问servlet,则需要将欢迎文件更改为指向 FileCounter servlet,而不是使用这些默认的欢迎文件

答案 3 :(得分:0)

只需在web.xml中添加 FileCounter 作为'welcome-file'之一

答案 4 :(得分:0)

您所指的教程使用的是动态Web模块版本2.5,而您可能正在使用3.0。 仔细看看你的web.xml,你会发现那里没有创建servlet映射。如果您不使用eclipse的默认servlet创建工具,可能会发生这种情况。这是我的web.xml看起来像:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>com.vogella.web.filecounter</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>FileCounter</servlet-name>
        <servlet-class>com.vogella.web.filecounter.servlet.FileCounter</servlet-class> 
    </servlet>

    <servlet-mapping>
        <servlet-name>FileCounter</servlet-name>
        <url-pattern>/FileCounter</url-pattern>
    </servlet-mapping>
</web-app>