Servlet + JavaBean 存取 MySQL 完整實戰教學

環境配置 (JDK 5.0 + Tomcat 5.5.4)

• JAVA_HOME=D:\Java\jdk1.5.0_01
• PATH=%JAVA_HOME%\bin
• CLASSPATH=.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar;D:\Tomcat 5.5\common\lib\servlet-api.jar;D:\Tomcat 5.5\common\lib\mysql-connector-java-3.1.6-bin.jar

Tomcat 虛擬目錄設定

D:\Tomcat 5.5\conf\Catalina\localhost\test.xml：

<Context path="/test" docBase="d:/www" reloadable="true" crossContext="true" debug="0" />

d:\www\WEB-INF\web.xml 參考 ROOT 應用，含 classes、lib 目錄。

資料庫連線 Bean (dbconn.java)

package NinGoo;
import java.sql.*;
public class dbconn {
    private Connection conn;
    private String URL = "jdbc:mysql://127.0.0.1:3306/test?user=root&password=password";
    private String driver = "com.mysql.jdbc.Driver";
    public Connection getConn() {
        try { Class.forName(driver).newInstance(); conn = DriverManager.getConnection(URL); }
        catch (Exception e) { e.printStackTrace(); }
        return conn;
    }
    public ResultSet executeSQL(String sql) {
        try { return conn.createStatement().executeQuery(sql); }
        catch (Exception e) { e.printStackTrace(); return null; }
    }
}

編譯後置於 D:\www\WEB-INF\classes\NinGoo\dbconn.class。

Servlet 呼叫 Bean (welcome.java)

public class welcome extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
        res.setContentType("text/html");
        NinGoo.dbconn bean = new NinGoo.dbconn();
        ResultSet rs = bean.executeSQL("select * from test");
        PrintWriter out = res.getWriter();
        out.println("<html><body>");
        while (rs.next()) out.println(rs.getString(1) + "<br>");
        out.println("successful!</body></html>");
    }
}

編譯置於 D:\www\WEB-INF\classes\welcome.class。

web.xml 註冊 Servlet

<servlet>
  <servlet-name>welcome</servlet-name>
  <servlet-class>welcome</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>welcome</servlet-name>
  <url-pattern>/welcome</url-pattern>
</servlet-mapping>

重啟 Tomcat，瀏覽 https://localhost:8080/test/welcome 即見資料庫查詢結果。