参考文档:https://www.cnblogs.com/wang-yaz/p/9340156.html
参考文档:http://www.pianshen.com/article/5023380349/
首先我们需要明白使用@Autowired注入的三种方式:
@Service("accountEmailService")
2 public class AccountEmailServiceImpl implements AccountEmailService{
3
4
5 /** 通过构造器注入---begin **/
6 private JavaMailSender javaMailSender;
7
8 @Autowired
9 public AccountEmailServiceImpl(JavaMailSender javaMailSender){
10 this.javaMailSender = javaMailSender;
11 }
12
13
14 /** 通过set方法注入---begin **/
15 private JavaMailSender javaMailSender;
16 @Autowired
17 public void setJavaMailSender(JavaMailSender javaMailSender){
18 this.javaMailSender = javaMailSender;
19 }
20
21
22 /** 通过field注入 **/
23 @Autowired
24 private JavaMailSender javaMailSender;
25
Spring是推荐使用构造器注入的:
Spring Team recommends: “Always use constructor based dependency injection in your beans. Always use assertions for mandatory dependencies”.
因为field注入有可能会出现NullPointerException
class MyComponent {
@Inject MyCollaborator collaborator;
public void myBusinessMethod() {
collaborator.doSomething(); // -> NullPointerException
}
}
但是构造器注入就是因为代码不够简洁才别我们弃之不用的。而用属性注入其实我们一直在用也没出错。所以有两种解决办法:
第一种:将“@Autowired”注解换为“@Resouce”注解。
@Resource是JSR-250规范中的注解,目前Spring已支持该规范。@Resource是先根据Bean的名称去匹配Bean,获取不到的话再根据类型去匹配;而@Autowired则是根据类型匹配,通过名称则需要Spring的@Qualifier注解配合。
第二种:修改setting里面对field注入的检查:setting->editor->code style->inspection-> spring->spring core-> code,去掉钩: