<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK"/>
<title>checkUser</title>
</head>
<body>
<%
String username=request.getParameter("username");
DBMS_Conn conn=new DBMS_Conn();
if(conn.checkUser(username))
out.println("用户名已经存在！");
//这个信息就是发送到前台去显示的信息，即服务器返回的信息
else
out.println("可以继续！");
%>
</body>
</html>
数据库连接JAVA程序：
package project1;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBMS_Conn {
Connection conn;
Statement st;
public DBMS_Conn() {
conn_init();
}
void conn_init() {
setConnection();
setStatement();
}
public void setConnection() {
try {
//Class.forName("org.gjt.mm.mysql.Driver").newInstance();
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
//db.mdb有一个名为user表，至少有一个名为username的字段
String strurl =
"jdbc:odbc:driver={Microsoft Access Driver (*.mdb)};DBQ=E:\\db.mdb";
//conn=DriverManager.getConnection("jdbc:mysql://localhost/palfinger?
//user=root&password=admin&useUnicode=true&characterEncoding=8859_1");
conn = DriverManager.getConnection(strurl);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 设置Statement
*/
public void setStatement() {
try {
st = conn.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 根据用户名确定用户是否存在
*/
public boolean checkUser(String username) {
String sql="select * from user where username='"+username+"'";
ResultSet rs;
try {
rs = st.executeQuery(sql);
if(rs.next())
{
conn.close();
return true;
}
} catch (SQLException e) {
e.printStackTrace();
}
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return false;
}
}
