Anschließen an database in Servlets

Ein servlet kann eines oder mehrer Connectionobject in seiner init () Methode verursachen und sie in seinem Service (), im doGet () und doPost () in den Methoden wiederverwenden. Um zu zeigen, zeigt Beispiel 9-4 das Telefonnachschlagen servlet, das neu geschrieben wird um seine Anschlußgegenstände im voraus zu verursachen. Es verwendet auch HtmlSQLResult, um die Resultate anzuzeigen. Merken, daß dieses servlet den Sybase JDBC Treiber benutzt.

Servlets Datenbank-Anschluß mit Mysql Datenbank

// File: ShowBedrock.java

/* A servlet to display the contents of the MySQL Bedrock database */

import java.io.*;
import java.net.*;
import java.sql.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ShowBedrock extends HttpServlet
{
public String getServletInfo()
{
return "Servlet connects to MySQL database and displays result of a SELECT";
}

// Use http GET

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
String loginUser = "Dude1";
String loginPasswd = "SuperSecret";
String loginUrl = "jdbc:mysql://localhost:3306/bedrock";

response.setContentType("text/html"); // Response mime type

// Output stream to STDOUT
PrintWriter out = response.getWriter();

out.println("<html><head><title>Bedrock</title></head>");
out.println("<body><h1>Bedrock</h11>");

// Load the mm.MySQL driver
try
{
Class.forName("org.gjt.mm.mysql.Driver");
Connection dbcon = DriverManager.getConnection(loginUrl, loginUser, loginPasswd);
// Declare our statement
Statement statement = dbcon.createStatement();

String query = "select name, dept, ";
query += " jobtitle ";
query += "from employee ";

// Perform the query
ResultSet rs = statement.executeQuery(query);

out.println("<table border>");

// Iterate through each row of rs
while (rs.next())
{
String m_name = rs.getString("name");
String m_dept = rs.getString("dept");
String m_jobtitle = rs.getString("jobtitle");
out.println("<tr>" +
"<td>" + m_name + "</td>" +
"<td>" + m_dept + "</td>" +
"<td>" + m_jobtitle + "</td>" +
"</tr>");
}

out.println("</table>");

rs.close();
statement.close();
dbcon.close();
}
catch (SQLException ex) {
while (ex != null) {
System.out.println ("SQL Exception: " + ex.getMessage ());
ex = ex.getNextException ();
} // end while
} // end catch SQLException

catch(java.lang.Exception ex)
{
out.println("<html>" +
"<head><title>" +
"Bedrock: Error" +
"</title></head>\n<body>" +
"<p>SQL error in doGet: " +
ex.getMessage() + "</p></body></html>");
return;
}
out.close();
}
}