Servlet未連接到數據庫

Question

所以我有一個書店網站。相關代碼如下：

的index.jsp（I具有的div，其中，foo是一本書的關鍵詞的幾個塊）

<form action="bookServlet" method="post"> 

      <div id='foo' style="float: left; width:25%"> 
       <img src ="${pageContext.request.contextPath}/images/foo.jpg" width ='200' height ='310' id ="foo" /> <br /> 
       Title of a Book <br /> 
       $7.99 <br /> 
       <input type= 'text' name= 'foo' size = 1 /> 
       <input type ='submit' name ='fooBtn' value ='Buy' onclick = 'this.disabled = true; return true;'/> <br /> <br /> 
      </div> 

bookServlet.java（I具有幾個每本書的if語句，再一個塊）

public class bookServlet extends HttpServlet { 

    public Statement statement; 
    static boolean flag[] = {false, false, false, false, false, false, false, 
     false, false, false, false, false, false, false, false, false}; 


    protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException, ClassNotFoundException, SQLException { 

     try { 
      Class.forName("oracle.jdbc.driver.OracleDriver"); 
      Connection connection = DriverManager.getConnection 
       ("url exactly as my professor gave me", "username", "password"); 
      System.out.print("Connected"); 
      statement = connection.createStatement(); 
     } 
     catch (Exception e){ 
      System.out.print("Could not connect"); 
     } 
     if (request.getParameter("fooBtn") != null) { 
     flag[0] = true; 
     String queryString = "select stock from Inventory where title = 'foo'"; 
     ResultSet result = statement.executeQuery(queryString); 
     int quantity = Integer.parseInt(request.getParameter("foo")); 
     int stock = result.getInt(1); 
     stock -= quantity; 
     String insertString = "insert into Cart(title, items, price) values('foo', 1, 7.99)"; 
     statement.executeUpdate(insertString); 
     String updateString = "update Inventory set stock = " + stock + " where title = 'foo'"; 
     statement.executeUpdate(updateString); 
     } 
    } 
} 

當我執行的index.jsp，它正確地顯示，但是當我試圖購買的一本書，它不連接到數據庫，更不用說更新它，或將標誌設置爲true。我不明白我做錯了什麼。

編輯：web.xml中

<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="3.0" 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_3_0.xsd"> 
    <servlet> 
     <servlet-name>bookServlet</servlet-name> 
     <servlet-class>books.bookServlet</servlet-class> 
    </servlet> 
    <servlet> 
     <servlet-name>checkoutServlet</servlet-name> 
     <servlet-class>books.checkoutServlet</servlet-class> 
    </servlet> 
    <servlet-mapping> 
     <servlet-name>bookServlet</servlet-name> 
     <url-pattern>/bookServlet</url-pattern> 
    </servlet-mapping> 
    <servlet-mapping> 
     <servlet-name>checkoutServlet</servlet-name> 
     <url-pattern>/checkoutServlet</url-pattern> 
    </servlet-mapping> 
    <session-config> 
     <session-timeout> 
      30 
     </session-timeout> 
    </session-config> 
</web-app> 

Answer 1

嘗試改變processRequest到service。

甲Servlet有3種狀態：

1. 該servlet通過調用init()方法初始化。這隻叫一次。
2. 然後，servlet調用service()方法來處理客戶端的請求。
3. 通過調用destroy()方法終止servlet。

如果您共享的代碼是完整的。那麼你錯過了service()方法。您可以使用doPost()和doGet()來處理客戶端請求。

我使用Oracle數據庫，我得到使用此連接對象：

Connection conn = DriverManager.getConnection 
    ("jdbc:oracle:thin:@myhost:1521:orcl", "scott", "tiger"); 

檢查您的網址。

Answer 2

如果您使用service/doPost或doGet方法來調用servlet中的processRequest方法，那麼很好，&好。但是，如果你沒有，就創造它&呼叫服務processRequest方法來獲得DB連接

Answer 3

您可以在任一這三個重載函數的編寫代碼

@Override 
protected void service(HttpServletRequest arg0, HttpServletResponse arg1) 
     throws ServletException, IOException { 
    //your processRequest code 
} 

@Override 
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    //your processRequest code 
} 

@Override 
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    //your processRequest code 
}