按照 user2821894 的建议，我能够使我的应用程序再次运行，但在尝试调用 servlet tomcat 7 后再次停止运行!! 如果我尝试删除调用我的 servlet 的代码，我的网络应用程序就无法正常工作!! 一旦我有一个 servlet tomcat 停止工作的问题。

我在 eclipse 上启动我的 web 项目时遇到了问题。我在使用 Tomcat 7 时遇到了问题。 所以我从 eclipse 中“删除”了 tomcat 7，然后我再次添加了它(再次是 tomcat 7)。

现在我启动我的 web 项目没有问题，但我的 servlet 有问题。 例如我收到类似

 WebServlet cannot be resolved to a type
 The attribute value is undefined for the annotation type 

我将 servlet-api 3.0.jar 添加到我的项目中，但我仍然遇到这些问题。

这是我的servlet的代码

 package Jeans;
    import java.io.IOException;
    import java.io.InputStream;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.SQLException;

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

    import com.sun.java.swing.plaf.windows.TMSchema.Part;


    import javax.servlet.http.Part;



    @WebServlet("/FileUploadDBServlet ")

  //// i got an error here//////////////////////////// 
    @MultipartConfig(maxFileSize = 16177215)  

    public class FileUploadDBServlet extends HttpServlet {


        private String dbURL = "db";
        private String dbUser = "dbuser";
        private String dbPass = "dbpassword";
        String messageMio = "da contorllare";  
        GestioneDB gestioneDB;
        boolean connessione;       
        Connection conn;

        protected void doPost(HttpServletRequest request,
                HttpServletResponse response) throws ServletException, IOException {




         String giorno= request.getParameter("giorno");
         String mese= request.getParameter("mese");
         String anno= request.getParameter("anno");         
         String dataFormatoItaliano = giorno + "-" + mese + "-" + anno;     

          String titolo = request.getParameter("titolo");
          String titoletto = request.getParameter("titoletto");
          String testoMouse = request.getParameter("testoMouse");
          String link = request.getParameter("link");
          String data = dataFormatoItaliano;
          String testo = request.getParameter("testo");




          //// i got an error here////////////////////////////
          Part filePart = request.getPart("immaginePrincipale");  






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


            InputStream immaginePrincipale = null; 
            if (filePart != null) {             
                // obtains input stream of the upload file
                immaginePrincipale = filePart.getInputStream();
            }





            String message = null;  

            try {

                  gestioneDB = new GestioneDB(); 
                  conn = gestioneDB.cn();  



                  gestioneDB.inserimentoNews(titolo, titoletto, testoMouse, link, testo, data, immaginePrincipale, didascaliaImmaginePrincipale);



                String sql = "INSERT INTO allegati_news (allegato,didascalia,tipo,id_news,immagine) values (?,?,?,?,?)";




                PreparedStatement statement = conn.prepareStatement(sql);
                statement.setString(1, "firstName");
                statement.setString(2, "lastName");
                statement.setInt(3, 1);
                statement.setInt(4,1);            
                if (immaginePrincipale != null) {              
                    statement.setBlob(5, immaginePrincipale);             
                }




                int row = statement.executeUpdate();
                if (row > 0) {
                    message = "File salvato nel db";
                }
            } catch (SQLException ex) {
                message = "ERROR: " + ex.getMessage();
                ex.printStackTrace();
            } finally {
                if (conn != null) {

                    try {
                        conn.close();
                    } catch (SQLException ex) {
                        ex.printStackTrace();
                    }
                }

               request.setAttribute("Message", gestioneDB.getInserimentoNewMessaggio());



               getServletContext().getRequestDispatcher("/Message.jsp").forward(request, response);
            }
        }
    }

这是我的 web.xml 文件

<?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_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Jeans2</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>
    <description></description>
    <display-name>prova</display-name>
    <servlet-name>prova</servlet-name>
    <servlet-class>Jeans.prova</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>prova</servlet-name>
    <url-pattern>/prova</url-pattern>
  </servlet-mapping>
  <servlet>

    <description></description>
    <display-name>FileUploadDBServlet</display-name>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>Jeans.FileUploadDBServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <url-pattern>/FileUploadDBServlet</url-pattern>
  </servlet-mapping>

   <servlet>
    <description></description>
    <display-name>BlobDisplay</display-name>
    <servlet-name>BlobDisplay</servlet-name>
    <servlet-class>Jeans.BlobDisplay</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobDisplay</servlet-name>
    <url-pattern>/BlobDisplay</url-pattern>
  </servlet-mapping>


</web-app>