servlet與資料庫連接

最後更新：2018-12-03 來源：互聯網

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//用於互動的html文檔

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Survey</title>
</head>
<body>
<form method="post" action="animalSurvey">
<p>What is your favorites pet?</p>
<p>
<input type="radio" name="animal" value="1" />Dog<br />
<input type="radio" name="animal" value="2" />Cat<br />
<input type="radio" name="animal" value="3" />Bird<br />
<input type="radio" name="animal" value="4" />Snake<br />
<input type="radio" name="animal" value="5" checked="checked" />Null<br />
</p>
<p><input type="submit" value="Submit" /></p>
</form>
</body>
</html>

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.DecimalFormat;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class SurveyServlet
* 資料庫由自己指定，自己設定databaseDriver，和databaseName就可以了，在web.xml中設定
* 資料庫名稱為surveyresults包含id,name,votes資料項目
*/
public class SurveyServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

private Connection connection;
private Statement statement;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SurveyServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

/**
* @see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
  // TODO Auto-generated method stub
  try {
   System.setProperty("Odbc", "E:/Eclpise/code/DataBase/data");//描述資訊

   Class.forName(config.getInitParameter("databaseDriver"));//串連資料庫
   connection=DriverManager.getConnection(config.getInitParameter("databaseName"));

   statement=connection.createStatement();
  } catch (Exception exception) {
   // TODO: handle exception
   exception.printStackTrace();
   throw new UnavailableException(exception.getMessage());
  }
}

/**
* @see Servlet#destroy()
*/
public void destroy() {
  // TODO Auto-generated method stub
  try {
   statement.close();
   connection.close();
  } catch (SQLException sqlException) {
   // TODO: handle exception
   sqlException.printStackTrace();
  }
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  response.setContentType("text/html");

  PrintWriter out=response.getWriter();
  DecimalFormat twoDigits=new DecimalFormat("0.00");

  out.println("<html>");
  out.println("<head>");

  int value=Integer.parseInt(request.getParameter("animal"));
  String query;

  try {
   //更新投票數
   query="UPDATE surveyresults SET votes=votes+1 "+"WHERE id="+value;
   statement.execute(query);

      //求出投票總數
   query="SELECT sum(votes)FROM surveyresults";
   ResultSet totalRS=statement.executeQuery(query);
   totalRS.next();
   int total=totalRS.getInt(1);

   query="SELECT id,name,votes FROM surveyresults "+"ORDER BY id";
   ResultSet resultSet=statement.executeQuery(query);
   out.println("<title>Thank you for participating</title>");
   out.println("</head>");
   out.println("<body>");
   out.println("<p>Thank you!");
   out.println("</ br>Results:</p><pre>");

   int votes;

   while (resultSet.next()) {
    out.print(resultSet.getString(2));
    out.print(": ");
       votes=resultSet.getInt(3);
       out.print(twoDigits.format((double)votes/total*100));
       out.print("% responses: ");
       out.println(votes);
   }

   resultSet.close();

   out.print("Total responses: ");
   out.print(total);

   out.println("</pre></body></html>");
   out.close();
  } catch (SQLException sqlException) {
   // TODO: handle exception
   sqlException.printStackTrace();
   out.println("<title>Error</title>");
   out.println("</head>");
   out.println("<body><p>DataBase error occured.");
   out.println("Try again later.</p></body></html>");
   out.close();
  }
}

}

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