querydbhandler.java

scwcd的考试,测试代码,如果希望参加此类考试将非常的有帮助

package scwcd.ch12.taglib;
import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.PrintWriter;
import java.sql.*;

public class QueryDBHandler extends TagSupport {
  Connection conn = null;
  Statement stmt = null;
  ResultSet rs = null;
  String driver_type;
  String url;
  String username;
  String password;
  String queryString;
  int rowCount = 10;

  public void setDriver_type(String newDriver_type){
    driver_type = newDriver_type;
  }
  public void setUrl(String newUrl){
    url = newUrl;
  }
  public void setUsername(String newUsername){
    username = newUsername;
  }
  public void setPassword(String newPassword){
    password = newPassword;
  }
  public String getQueryString() {
    return queryString;
  }
  public void setQueryString(String newQueryString){
    queryString = newQueryString;
  }
  public void setRowCount(int newRowCount){
    rowCount = newRowCount;
  } 
  
  public int doStartTag() throws JspException {
    try{
      JspWriter out = pageContext.getOut();
      Class.forName(driver_type);
      Connection conn = 
         DriverManager.getConnection(url, username, password);
      Statement stmt = conn.createStatement ();    
      ResultSet rset = stmt.executeQuery (queryString);
      ResultSetMetaData md = rset.getMetaData();
    
      int no_cols = md.getColumnCount(); 
      String[] col_names = new String[no_cols];
    
      for(int i = 0; i < no_cols; i++)
        col_names[i] = md.getColumnLabel(i+1);

      out.println("<table border=1>");
      out.println("<tr>");

      for(int i = 0; i < no_cols; i++) { 
        out.println("<td bgcolor='#008080'>");
        out.println("<font color='#FFFFFF'>");
        out.println(col_names[i]);
        out.println("</font></td>");
      }
      out.println("</tr>");

      while (rset.next ()) { 
        out.println("<tr>");
        for(int i = 1; i <= no_cols; i++) { 
          out.println("<td>" + rset.getString(i) + "</td>");
        } 
        out.println("</tr>");
        if (--rowCount ==0) break;    
      }
    }
    catch(Exception e){
      e.printStackTrace();
    }
    return SKIP_BODY;
  }
  public int doAfterBody() throws JspException {
    return SKIP_BODY;
  }
  public int doEndTag() {
    return EVAL_PAGE;
  }
}