如何使用单例模式返回一个安全的Connection

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectDemo {
public enum MyEnumSingleton {

connectionFactory;
private Connection conn;

private MyEnumSingleton() {
try {
String url = "jdbc:mysql://localhost:3306/mydb";
String name = "root";
String password = "";
String Driver = "com.mysql.jdbc.Driver";

Class.forName(Driver);

conn = DriverManager.getConnection(url, name, password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public Connection getConn() {
return conn;
}

}

public static Connection getConn() {
return MyEnumSingleton.connectionFactory.getConn();
}

}

使用枚举类时，构造方法会被自动调用。

再修改一下，降低一下耦合度，将建立连接的四大参数改成在配置文件中获取

首先在项目目录下建立一个配置文件



把参数添加进去

变成从配置文件中读取参数，这样修改的话只用修改配置文件就可以了

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class ConnectDemo {
public enum MyEnumSingleton {

connectionFactory;
private Connection conn;

private MyEnumSingleton() {
try {
InputStream in=Connection.class.getClassLoader()
.getResourceAsStream("dbconfig.properties");
Properties pro=new Properties();
pro.load(in);
String url = pro.getProperty("url");
String name = pro.getProperty("name");
String password =pro.getProperty("password");
String Driver = pro.getProperty("DriverClassName");

Class.forName(Driver);

conn = DriverManager.getConnection(url, name, password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}
}

public Connection getConn() {
return conn;
}

}

public static Connection getConn() {
return MyEnumSingleton.connectionFactory.getConn();
}

}