从Java Servlet执行MySQL命令

我试图让我的servlet输出用户输入的SQL命令的结果。此时，servlet可以正确检测到某个命令何时不包含“SELECT”，“INSERT”或“DELETE”，并输出错误消息。当命令有效时，不输出任何内容。我知道这意味着我的问题可能发生在我尝试连接到数据库的位置，或者我试图将输出打印到“out”的位置。从Java Servlet执行MySQL命令

databaseServlet.java

import javax.servlet.*; 
import javax.servlet.http.*; 
import java.io.*; 
import java.sql.*; 

@SuppressWarnings("serial") 
public class databaseServlet extends HttpServlet { 
    private Connection conn; 
    private Statement statement; 

    public void init(ServletConfig config) throws ServletException { 
     try { 
      Class.forName(config.getInitParameter("databaseDriver")); 
      conn = DriverManager.getConnection(
        config.getInitParameter("databaseName"), 
        config.getInitParameter("username"), 
        config.getInitParameter("password")); 
      statement = conn.createStatement(); 
     } 
     catch (Exception e) { 
      e.printStackTrace(); 
     } 
    } 

    protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     response.setContentType("text/html"); 
     PrintWriter out = response.getWriter(); 

     out.println("<xml version = \"1.0\"?>"); 
     out.println("<!DOCTYPE html PUBLIC \"-//W3C//DTD " + 
      "XHTML 1.0 Strict//EN\" \"http://www.w3.org" + 
      "/TR/xhtml1/DTD/xhtml1-strict.dtd\">"); 
     out.println("<html xmlns = \"http://www.w3.org/1999/xhtml\">"); 
     out.println("<head>"); 
     out.println("<title>MySQL Servlet</title>"); 
     out.println("<style type='text/css'>"); 
     out.println("body{background-color: blue}"); 
     out.println("</style>"); 
     out.println("</head>"); 
     out.println("<body>"); 

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

     if (query.toLowerCase().contains("select")) { 
      //SELECT Queries 
      try { 
       ResultSet resultSet = statement.executeQuery(query); 
       ResultSetMetaData metaData = resultSet.getMetaData(); 
       int numberOfColumns = metaData.getColumnCount(); 
       for(int i = 1; i<= numberOfColumns; i++){ 
        out.printf("%20s\t", metaData.getColumnName(i)); 
       } 
       out.println(); 

       while (resultSet.next()){ 
        for (int i = 1; i <= numberOfColumns; i++){ 
         out.printf("%20s\t", resultSet.getObject(i)); 
        } 
        out.println(); 
       } 
      } 
      catch (Exception f) { 
       f.printStackTrace(); 
      } 
     } 
     else if (query.toLowerCase().contains("delete") || query.toLowerCase().contains("insert")) { 
      //DELETE and INSERT commands 
      try { 
       conn.prepareStatement(query).executeUpdate(query); 
       out.println("\t\t Database has been updated!"); 
      } 
      catch (Exception l){ 
       l.printStackTrace(); 
      } 
     } 
     else { 
      //Not a valid response 
      out.println("\t\t Not a valid command or query!"); 
     } 

     out.println("</body>"); 
     out.println("</html>"); 
     out.close(); 
    } 
}

dbServlet.jsp

<?xml version = "1.0"?> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<!-- dbServlet.html --> 
<html xmlns = "http://www.w3.org/1999/xhtml"> 
<head> 
    <title>MySQL Servlet</title> 
    <style type="text/css"> 
     body{background-color: green;} 
    </style> 
</head> 
<body> 
    <h1>Hello World!</h1> 
    <h2>This is the MySQL Servlet</h2> 
    <form action = "/database/database" method = "get"> 
    <p> 
     <label>Enter your query and click the button to invoke a MySQL Servlet 
      <input type = "text" name = "query" /> 
      <input type = "submit" value = "Run MySQL Servlet" /> 
     </label> 
    </p> 
    </form> 
</body> 
</html>

我认为另一个潜在的故障点可能是我的路径数据库文件，这是在我的web.xml文件初始化。我在网上找到的一个例子包括端口，但我想知道是否应该删除端口号。有谁知道用于MySQL的默认端口？

这是我说的是从下面的xml文件的具体线路：的jdbc：mysql的：//本地主机：3309/project4

的web.xml

<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> 
    <!-- General description of the web application --> 
    <display-name> 
    MySQL Servlet 
    </display-name> 
    <description> 
    This web application allows the user to connect to a database, sumbit queries, and make changes. 
    </description> 
    <!-- Servlet definitions --> 
    <servlet> 
    <servlet-name>database</servlet-name> 
    <description> 
     A servlet that handles SQL commands submitted by the user. 
    </description> 
    <servlet-class> 
     databaseServlet 
    </servlet-class> 
    <init-param> 
     <param-name>databaseDriver</param-name> 
     <param-value>com.mysql.jdbc.Driver</param-value> 
    </init-param> 
    <init-param> 
     <param-name>databaseName</param-name> 
     <param-value>jdbc:mysql://localhost:3309/project4</param-value> 
    </init-param> 
    <init-param> 
     <param-name>username</param-name> 
     <param-value>root</param-value> 
    </init-param> 
    <init-param> 
     <param-name>password</param-name> 
     <param-value>pass</param-value> 
    </init-param> 
    </servlet> 
    <servlet-mapping> 
    <servlet-name>database</servlet-name> 
    <url-pattern>/database</url-pattern> 
    </servlet-mapping> 
</web-app>

来源

2012-11-15 PeerPressure

在servlet中写入HTMl的方式太旧了，认为是坏的。 – PermGenError

你是对的！这只是我测试数据库的原型。最终版本将只输出查询结果到jsp前端页面（只有用户会看到的页面），其中将包含所有html元素。我只想让数据库级别的工作，并知道我有正确的输出，在最终确定的前端。 – PeerPressure

我真的很希望你的最终版本也不会接受SQL作为GET参数。仅仅看到这一点，就让我感到脊柱寒冷起来。 – Kenny

我用口3309，并在需要使用端口3306

问题

jdbc:mysql://localhost:3309/project4

小号OLUTION

jdbc:mysql://localhost:3306/project4

来源

2012-11-15 22:41:09 PeerPressure

从Java Servlet执行MySQL命令

回答

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