Java code
public class DBHelper {
Private String drivername;
Private String URL;
Private String user;
private String password;
Private Connection Connection;
Private String Createtablesql;
Private String Droptablesql;
public void getconnection () {
if (null = = connection) {
try {
Class.forName (drivername);
Connection = drivermanager.getconnection (URL, user, password);
} catch (ClassNotFoundException | SQLException e) {
E.printstacktrace ();
}
}
}
public void CloseConnection () {
if (null! = connection) {
try {
Connection.close ();
connection = null; Connection.close won ' t set the connection to IS null
System.out.println ("Closed DB connection.");
} catch (SQLException e) {
E.printstacktrace ();
}
}
}
public void CreateTable () {
Getconnection ();
Statement stmt = null;
try {
stmt = Connection.createstatement ();
Stmt.execute (Createtablesql);
SYSTEM.OUT.PRINTLN ("Executed SQL [" + Createtablesql + "] success.");
} catch (SQLException e) {
E.printstacktrace ();
}
CloseConnection ();
}
public void droptable () {
Getconnection ();
Statement stmt = null;
try {
stmt = Connection.createstatement ();
Stmt.execute (Droptablesql);
SYSTEM.OUT.PRINTLN ("Executed SQL [" + Droptablesql + "] success.");
} catch (SQLException e) {
E.printstacktrace ();
}
CloseConnection ();
}
Public String Getdrivername () {
return drivername;
}
public void Setdrivername (String drivername) {
This.drivername = drivername;
}
Public String GetUrl () {
return URL;
}
public void SetUrl (String URL) {
This.url = URL;
}
Public String GetUser () {
return user;
}
public void SetUser (String user) {
This.user = user;
}
Public String GetPassword () {
return password;
}
public void SetPassword (String password) {
This.password = password;
}
Public String Getcreatetablesql () {
return createtablesql;
}
public void Setcreatetablesql (String createtablesql) {
This.createtablesql = Createtablesql;
}
Public String Getdroptablesql () {
return droptablesql;
}
public void Setdroptablesql (String droptablesql) {
This.droptablesql = Droptablesql;
}
}
Java code
<%@ page language= "java" contenttype= "text/html; Charset=utf-8 "
pageencoding= "UTF-8"%>
<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 ">
<title>test connecting MySQL db</title>
<body>
<jsp:usebean id= "DBHelper" class= "Com.jesse.jsp.bean.DBHelper"/>
<jsp:setproperty property= "drivername" name= "DBHelper" value= "Com.mysql.jdbc.Driver"/>
<jsp:setproperty property= "url" name= "DBHelper" value= "jdbc:mysql://192.168.1.104:3306/db_jesse?useunicode= TRUE&CHARACTERENCODING=GBK "/>
<jsp:setproperty property= "user" name= "dbhelper" value= "Jesse"/>
<jsp:setproperty property= "Password" name= "DBHelper" value= "Jesse"/>
<jsp:setproperty property= "Createtablesql" name= "DBHelper" value= "CREATE TABLE test_tbl (id int)"/>
<jsp:setproperty property= "Droptablesql" name= "DBHelper" value= "drop table Test_tbl"/>
<%!
private int id = 0;
%>
<%
System.out.println (this); To check if the servlet is singleton
id++;
Synchronized (Com.jesse.jsp.bean.DBHelper.class) {
Dbhelper.createtable ();
System.out.println (ID + "created the table.");
Thread.Sleep (5000);
Dbhelper.droptable ();
System.out.println (ID + "dropped the table.");
}
%>
</body>
Java code
[Email protected]
Executed SQL [CREATE TABLE TEST_TBL (ID int)] success.
Closed DB connection.
1 created the table.
[Email protected]
Executed SQL [drop table TEST_TBL] success.
Closed DB connection.
2 dropped the table.
Executed SQL [CREATE TABLE TEST_TBL (ID int)] success.
Closed DB connection.
2 created the table.
Executed SQL [drop table TEST_TBL] success.
Closed DB connection.
2 dropped the table.
Note: The intention is to let the log print out which session is executing, see the results ... Long knowledge, <%!. %> looked down, think this statement has reason, temporarily do not drill down: <%%> is the code snippet, after the conversion from JSP to servlet <%%> code is placed in the Serive method, equivalent to Doget () and Dopost () method <%!% > is a JSP declaration that defines properties and methods, and the code in <%!%> after conversion from JSP to servlet is outside the Serive method.
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JSP Simple Access database
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