@Autowired 自動注入空指針異常 ( 問題出現在了Junit單元測試 )

我用的Junit測試

寫法如下:

@Component
public class Test_SSM {
    @Autowired
    private UserService userService;
    
    @Test
    public void show() {
        System.out.println(userService);
    }
}
           

然後調用測試show方法

輸出為 null

隻需這樣改, 測試類上的兩行注解

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration( locations = "classpath:applicationContext.xml")
/*locations屬性值 為 spring 配置檔案路徑*/
           

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration( locations = "classpath:applicationContext.xml")
public class Test_SSM {
    @Autowired
    private UserService userService;
    
    @Test
    public void show() {
        System.out.println(userService);
    }
}