JDBCInitServlet.java
codice:import java.io.*; import java.sql.*; import javax.servlet.*; import javax.servlet.http.*; public class JDBCInitServlet extends SimpleInitServlet { protected Connection conn = null; @Override public void init(ServletConfig config) throws ServletException { super.init(config); try { // load JDBC driver Class.forName(mydriver).newInstance(); conn = DriverManager.getConnection(myurl, myuserID, mypassword); System.out.println("Connection successful.."); } catch (SQLException se) { System.out.println(se);} catch (Exception e) { e.printStackTrace(); } } public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("TEXT/HTML"); PrintWriter out = res.getWriter(); out.println("<HTML>"); out.println("<TITLE>JDBC Init Connection</TITLE>"); out.println("<BODY>"); try { executeSQL(out); } catch (SQLException se) { se.printStackTrace(); } out.println("</BODY></HTML>"); out.close(); } public void executeSQL(PrintWriter out) throws SQLException{ Statement stmt = conn.createStatement(); String sql = "SELECT * FROM DEPARTMENT"; stmt.executeQuery(sql); ResultSet rs = stmt.getResultSet(); int count = 1; while (rs.next()) { out.println(""+rs.getString("DEPTNAME")+" <BLOCKQUOTE>"); String sql2 = "SELECT * FROM EMPLOYEE WHERE WORKDEPT = '" + rs.getString("DEPTNO") + "'"; Statement stmt2 = conn.createStatement(); stmt2.executeQuery(sql2); ResultSet rs2 = stmt2.getResultSet(); while(rs2.next()) { out.println(rs2.getString("FIRSTNME") + " " + rs2.getString("LASTNAME") + " "); } out.println("</BLOCKQUOTE>"); } } }
codice:type Exception report message description The server encountered an internal error () that prevented it from fulfilling this request. exception java.lang.NullPointerException JDBCInitServlet.executeSQL(JDBCInitServlet.java:44) JDBCInitServlet.doGet(JDBCInitServlet.java:36) javax.servlet.http.HttpServlet.service(HttpServlet.java:621) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393) note The full stack trace of the root cause is available in the Apache Tomcat/7.0.22 logs.
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