自定义一个注解来获取数据库的链接

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface JdbcInfo {
String driverClass() default “com.mysql.jdbc.Driver”;
String url();
String username() default “root”;
String password() default “1012”;
}

import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;

public class JdbcUtils {
@JdbcInfo(url = “jdbc:mysql://localhost:3306/day16”)
public static Connection getConnection() throws Exception{
//获取字节码文件
Class clazz = JdbcUtils.class;
//获取getConnection()
Method method = clazz.getMethod(“getConnection”, null);
if(method.isAnnotationPresent(JdbcInfo.class)){//判断方法上是否有注解
//获取注解
JdbcInfo jdbcInfo = method.getAnnotation(JdbcInfo.class);
//获取四大参数
String driverClass = jdbcInfo.driverClass();
String url = jdbcInfo.url();
String username = jdbcInfo.username();
String password = jdbcInfo.password();
//注册驱动
Class.forName(driverClass);
Connection connection = DriverManager.getConnection(url, username, password);
//获取连接
return connection;
}
return null;
}
public static void main(String[] args) throws Exception {
System.out.println(getConnection());
}
}