3.Sprint 代理对象与原始对象的异常错误

Posted 2021-02-07 likevin

代码案例分析

• Service层添加了注解@Transactional

@Service
@Transactional
public class CustomerService extends BaseService<CustomerModel, CustomerQueryModel> implements ICustomerService {
    private CustomerDAO dao = null;
    @Autowired
    public void setDao(CustomerDAO dao) {
        this.dao = dao;
        super.setDao(dao);
    }
}

• Client端同时也增加了注解@Transactional

 

@Service
@Transactional
public class Client {
    @Autowired
    private ICustomerService s = null;
    
    public static void main(String[] args) {
        ApplicationContext ctx =  new ClassPathXmlApplicationContext("applicationContext.xml");
        
        Client t = (Client)ctx.getBean("client");
        
//        CustomerModel cm = new CustomerModel();
//        cm.setCustomerId("c1");
//        cm.setPwd("c1");
//        cm.setRegisterTime("");
//        cm.setShowName("c1");
//        cm.setTrueName("王五");
//        
//        t.dao.create(cm);
        
        CustomerQueryModel cqm = new CustomerQueryModel();
        cqm.getPage().setNowPage(1);
        
        
        Page<CustomerModel> p = t.s.getByConditionPage(cqm);
        
        System.out.println("p=="+p);
    }
}

 

• 异常空指针错误信息

Exception in thread "main" java.lang.NullPointerException
    at com.sishuok.architecture1.customermgr.Client.main(Client.java:38)

Client.java:38行报的异常错误信息，就是Page<CustomerModel> p = t.s.getByConditionPage(cqm);

经过分析，t对象肯定存在，只有s对象存在空指针，为什么呢？

原因是因为增加了@Transactional 之后，又被代理了一次，意思就是sprint的原始对象与代理对象的问题，s的原始对象是有的，但是t.s拿到的是@Transactional 代理过后的对象，t.s 和s 不是同一个对象，解决办法如下

 

@Service
@Transactional
public class Client {
    @Autowired
    private ICustomerService s = null;
    
    public ICustomerService getS() {
        return s;
    }
    
    public static void main(String[] args) {
        ApplicationContext ctx =  new ClassPathXmlApplicationContext("applicationContext.xml");
        
        Client t = (Client)ctx.getBean("client");
        
//        CustomerModel cm = new CustomerModel();
//        cm.setCustomerId("c1");
//        cm.setPwd("c1");
//        cm.setRegisterTime("");
//        cm.setShowName("c1");
//        cm.setTrueName("王五");
//        
//        t.dao.create(cm);
        
        CustomerQueryModel cqm = new CustomerQueryModel();
        cqm.getPage().setNowPage(1);
        
        
//        Page<CustomerModel> p = t.s.getByConditionPage(cqm);
        
        Page<CustomerModel> p = t.getS().getByConditionPage(cqm);
        
        System.out.println("p=="+p);
    }

一切正常，为什么可以解决？代理的时候通过方法进行访问（拦截的方法），属性的就没有正常的代理private ICustomerService s = null;