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, java.io.IOException {
String sql = "select * from aTable";
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
ResultSetMetaData rsm = null;
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
out
.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 {
stmt.close();
conn.close();
} catch (SQLException sqle) {
}
}
out.println("</table></body></html>");
out.close();
} //doGet
private void printMeta(ResultSetMetaData metaData, String type,
java.io.PrintWriter out, int colCount) throws SQLException {
if (metaData == null || type == null || out == null)
throw new IllegalArgumentException(
"Illegal args passed to printMeta()");
out.println("<tr>");
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) {
out
.println("<td>" + metaData.getColumnDisplaySize(i)
+ "</td>");
}
}
out.println("</tr>");
}//printMeta
}
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