连接数据库需要的步骤：

0.放入需要的jar包

1.DemoConfig的插件配置

public void configPlugin(Plugins me) {
//添加插件
me.add(new EhCachePlugin());

DruidPlugin druidPlugin = new DruidPlugin("jdbc:mysql://127.0.0.1:3306/jfinal_demo", "root","admin");
me.add(druidPlugin);

//激活插件
ActiveRecordPlugin activeRecordPlugin = new ActiveRecordPlugin(druidPlugin);
activeRecordPlugin.addMapping("user", UserModel.class); //需要自行创建UserModel类
me.add(activeRecordPlugin);
}

2.配置UserController类，进行操作

public void action1() {
System.out.println("<<<<<<<<<<<action1>>>>>>>>>");
//增
UserModel user = new UserModel();
user.set("name","JJJJJC");
user.set("password", 6987745);
user.save();
//通过id查询数据
UserModel dbModel = UserModel.DAO.findById(user.getLong("id"));


String name = user.getStr("name");
String password = user.getStr("password");
renderJson("name:"+name+" password:"+password);

}

 3.创建UserMode

public class UserModel extends Model<UserModel>{

private static final long serialVersionUID = 1L;
public static final UserModel DAO = new UserModel();
}