Database and Servlet: Database MetaData : Database « Servlets « Java

Database and Servlet: Database MetaData

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

public class DbMetaServlet extends HttpServlet {

  DataSource pool;

  public void init() throws ServletException {

    Context env = null;

    try {

      env = (Context) new InitialContext().lookup("java:comp/env");

      pool = (DataSource) env.lookup("jdbc/oracle-8i-athletes");

      if (pool == null)
        throw new ServletException(
            "'oracle-8i-athletes' is an unknown DataSource");

    } catch (NamingException ne) {

      throw new ServletException(ne);


  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, {

    String sql = "select * from aTable";
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;
    ResultSetMetaData rsm = null;

    response.setContentType("text/html"); out = response.getWriter();
        .println("<html><head><title>Discover a ResultSet</title></head><body>");
    out.println("<h2>Here is Info about the returned ResultSet</h2>");
    out.println("<table border='1'><tr>");

    try {

      //Get a connection from the pool
      conn = pool.getConnection();

      //Create a Statement with which to run some SQL
      stmt = conn.createStatement();

      //Execute the SQL
      rs = stmt.executeQuery(sql);

      //Get a ResultSetMetaData object from the ResultSet
      rsm = rs.getMetaData();

      int colCount = rsm.getColumnCount();

      //print column names
      printMeta(rsm, "name", out, colCount);

      //print column index
      printMeta(rsm, "index", out, colCount);

      //print column type
      printMeta(rsm, "column type", out, colCount);

      //print column display size
      printMeta(rsm, "column display", out, colCount);

    } catch (Exception e) {

      throw new ServletException(e.getMessage());

    } finally {

      try {


      } catch (SQLException sqle) {


  } //doGet

  private void printMeta(ResultSetMetaData metaData, String type, out, int colCount) throws SQLException {

    if (metaData == null || type == null || out == null)
      throw new IllegalArgumentException(
          "Illegal args passed to printMeta()");


    if (type.equals("table")) {

      out.println("<td><strong>Table name</strong></td>");

      for (int i = 1; i <= colCount; ++i) {

        out.println("<td>" + metaData.getTableName(i) + "</td>");

    } else if (type.equals("name")) {

      out.println("<td><strong>Column name</strong></td>");

      for (int i = 1; i <= colCount; ++i) {

        out.println("<td>" + metaData.getColumnName(i) + "</td>");

    } else if (type.equals("index")) {

      out.println("<td><strong>Column index</strong></td>");

      for (int i = 1; i <= colCount; ++i) {

        out.println("<td>" + i + "</td>");

    } else if (type.equals("column type")) {

      out.println("<td><strong>Column type</strong></td>");

      for (int i = 1; i <= colCount; ++i) {

        out.println("<td>" + metaData.getColumnTypeName(i) + "</td>");

    } else if (type.equals("column display")) {

      out.println("<td><strong>Column display size</strong></td>");

      for (int i = 1; i <= colCount; ++i) {

            .println("<td>" + metaData.getColumnDisplaySize(i)
                + "</td>");





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