java 空指针异常?好像逻辑有错

Question

public class ProductsResource01 {
private final Logger log = LoggerFactory.getLogger(this.getClass());

@Autowired
private ProductsService productsService;
public void getProductsList(){      
    List<Products> list = productsService.getAll();
    for(Products a : list){
        System.out.println(a);
    }
}

public static void main(String[] args) {
    ProductsResource01 p01 = new ProductsResource01();
    p01.getProductsList();
}

Bug信息：
Exception in thread "main" java.lang.NullPointerException
at cn.syy.otherUtils.ProductsResource01.getProductsList(ProductsResource01.java:18)
at cn.syy.otherUtils.ProductsResource01.main(ProductsResource01.java:26)

Answer 1

18行 productsService 这个对象是空的，没有注入进来。productsService 注解是@AutoWired 是有容器管理其生命周期的，如你直接用main来new ProductsResource01对象， productsService没有注进来，所以报空指针，这种做单元测试可以用Junit