1 在mybatis Guice 事務原始碼解析中，可以發現SqlSessionManager中的sqlSessionProxy使用SqlSession構建的代理

    private SqlSessionManager(SqlSessionFactory sqlSessionFactory) {
        this.sqlSessionFactory = sqlSessionFactory;
        this.sqlSessionProxy = (SqlSession)Proxy.newProxyInstance(SqlSessionFactory.class.getClassLoader(), new Class[]{SqlSession.class}, new SqlSessionManager.SqlSessionInterceptor());
    }

this.sqlSessionProxy = (SqlSession)Proxy.newProxyInstance(SqlSessionFactory.class.getClassLoader(), new Class[]{SqlSession.class}, new SqlSessionManager.SqlSessionInterceptor());

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private class SqlSessionInterceptor implements InvocationHandler {
    public SqlSessionInterceptor() {
 
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        SqlSession sqlSession = (SqlSession)SqlSessionManager.this.localSqlSession.get();
        if(sqlSession != null) {
            try {
                return method.invoke(sqlSession, args);
            } catch (Throwable var19) {
 
                throw ExceptionUtil.unwrapThrowable(var19);
            }
        } else {
            SqlSession autoSqlSession = SqlSessionManager.this.openSession();
            Throwable var6 = null;

            Object var8;
            try {
                try {
                    Object t = method.invoke(autoSqlSession, args);
                    autoSqlSession.commit();
                    var8 = t;
                } catch (Throwable var20) {
                    autoSqlSession.rollback();
                    throw ExceptionUtil.unwrapThrowable(var20);
                }
            } catch (Throwable var21) {
                var6 = var21;
                throw var21;
            } finally {
                if(autoSqlSession != null) {
                    if(var6 != null) {
                        try {
                            autoSqlSession.close();
                        } catch (Throwable var18) {
                            var6.addSuppressed(var18);
                        }
                    } else {
                        autoSqlSession.close();
                    }
                }

            }

            return var8;
        }
    }
}

可以看到沒有維護被代理的target物件，用的時候即時生成被代理的DefaultSqlSession物件

public class ProxyFactory implements InvocationHandler {
    //維護一個目標物件
    private Object target;
    public ProxyFactory(Object target){
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("開始事務jdk");
        Object returnValue = method.invoke(target, args);
        System.out.println("提交事務jdk");
        return returnValue;
    }

    //給目標物件生成代理物件
    public Object getProxyInstance(){
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
    }

}

public class ProxyFactoryNonTarget implements InvocationHandler {

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("開始事務jdk");
        Object returnValue = method.invoke(new UserDao(), args);
        System.out.println("提交事務jdk");
        return returnValue;
    }

    //給目標物件生成代理物件
    public Object getProxyInstance(){
        return Proxy.newProxyInstance(ProxyFactoryNonTarget.class.getClassLoader(), new Class[]{IUserDao.class}, this);
    }

}

下面的每次invoke都生成新物件

2 mybatis本身就是根據interface直接生成代理物件，沒有被代理物件，因為連被代理實現類都沒有