MySQL性能调优-3.MySQL存储引擎简介

代理模式

静态代理

• 目标类和代理类实现同一接口
• 对功能进行增强
• 缺点: 因为目标类和代理类实现了同一接口，此时接口一旦发生改变，两个类都必须同时实现新增的功能（动态代理可以解决这一缺点）

/**
 * @USER: lynn
 * @DATE: 2020/4/26
 **/
public class 静态代理 {
    public static void main(String[] args) {
        数学老师 mathTeacher1 = new 数学老师();
        数学教授 mathTeacher2 = new 数学教授(mathTeacher1);
        mathTeacher2.教书();
    }
}
interface 老师{
    void 教书();
}
class 数学老师 implements 老师{
    @Override
    public void 教书() {
        System.out.println("教数学");
    }
}

class 数学教授 implements 老师{

    private 数学老师 math;

    public 数学教授(数学老师 math) {
        this.math = math;
    }

    @Override
    public void 教书() {
        System.out.println("教物理");
        math.教书();
    }
}

动态代理

/**
 * @USER: lynn
 * @DATE: 2020/4/26
 **/
public class 动态代理 {
    public static void main(String[] args) {
        DynamicProxy dynamicProxy = new DynamicProxy(new 董事长(),new 助理());
        职工 worker = (职工)dynamicProxy.newInstance();
        worker.work();
    }
}
interface 职工{
    void work();
}
class 董事长 implements 职工{
    @Override
    public void work() {
        System.out.println("做董事长该干的事");
    }
}
class 助理 {
    public void beforeWork(){
        System.out.println("work前");
    }
    public void afterWork(){
        System.out.println("work后");
    }
}

class DynamicProxy{
    private Object object;
    private 助理 helper;

    public DynamicProxy(Object object, 助理 helper) {
        this.object = object;
        this.helper = helper;
    }

    public Object newInstance(){
        Class<?> clas = this.object.getClass();
        return Proxy.newProxyInstance(clas.getClassLoader(), clas.getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                helper.beforeWork();
                Object obj = method.invoke(object,args);
                helper.afterWork();
                return obj;
            }
        });
    }
}

Cglib代理

• Spring中AOP的实现原理就是用的代理模式–>动态代理+Cglib代理
  • 如果目标类实现了接口，Spring底层AOP就调用动态代理，否则调用Cglib代理

/**
 * @USER: lynn
 * @DATE: 2020/4/26
 **/
public class Cglib代理 {
    public static void main(String[] args) {
        CrudDaoInterceptor interceptor = new CrudDaoInterceptor(new CrudDaoImpl(),new Transaction());
        CrudDaoImpl proxy = (CrudDaoImpl) interceptor.getObject();
        proxy.delete();
    }

}
class CrudDaoImpl{
    public void select(){
        System.out.println("select * from table");
    }
    public void insert(){
        System.out.println("insert into table values()");
    }
    public void delete(){
        System.out.println("delete from table where id = ?");
    }
    public void update(){
        System.out.println("update table set id = ? where name = ?");
    }
}

class Transaction{
    public void openTransaction(){
        System.out.println("开启事务");
    }
    public void commitTransaction(){
        System.out.println("提交事务");
    }
}

class CrudDaoInterceptor implements MethodInterceptor{

    private Object object;
    private Transaction transaction; //切面

    public CrudDaoInterceptor(Object object, Transaction transaction) {
        this.object = object;
        this.transaction = transaction;
    }

    public Object getObject() {
        Enhancer enhancer = new Enhancer();
        Class<?> clazz = this.object.getClass();
        enhancer.setCallback(this);
        enhancer.setClassLoader(clazz.getClassLoader());
        enhancer.setInterfaces(clazz.getInterfaces());
        enhancer.setSuperclass(clazz);
        return enhancer.create();
    }

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        String methodName = method.getName();
        System.out.println("执行的方法名为:"+methodName);
        if ("delete".equals(methodName)){
            transaction.openTransaction();
            method.invoke(object,objects);
            transaction.commitTransaction();
        }

        return null;
    }
}

---

转载请注明来源，欢迎对文章中的引用来源进行考证，欢迎指出任何有错误或不够清晰的表达。可以在下面评论区评论，也可以邮件至 yanglau0527@gmail.com