new和@Autowired的区别

1. controller层:

   @RequestMapping("/payment")
   @RestController
   public class WxPayController {
   
       public WxPayServiceImpl wxPayService = new WxPayServiceImpl();
   
       @RequestMapping("/wxpay/{product_id}")
       public String getWxQrCode(@PathVariable("product_id") Integer productId) {
           System.out.println(productId);
           return wxPayService.getWxQrCode(productId);
       }
   }
   

   service层:

   @Service
   public class WxPayServiceImpl implements WxPayService {
   
       @Autowired
       public WxPayConfigBean wxPayConfigBean;
   
       @Override
       public String getWxQrCode(Integer productId) {
           System.out.println("wxPayConfigBean:" + wxPayConfigBean);
           HashMap<String, String> map = new HashMap<String,String>();
           map.put("appid",wxPayConfigBean.getAppID());
           map.put("mch_id",wxPayConfigBean.getMchID());
           //这里获得的是以秒为单位的时间戳
           Long timeStamp =  WXPayUtil.getCurrentTimestamp();
           map.put("time_stamp",timeStamp.toString());
           map.put("product_id",productId.toString());
           try {
               map.put("sign",WXPayUtil.generateSignature(map,wxPayConfigBean.getKey()));
           } catch (Exception exception) {
               exception.printStackTrace();
           }
           String str = "//wxpay/bizpayurl?"
                   + "sign=" + map.get("sign")
                   + "&appid=" + map.get("appid")
                   + "&mch_id= " + map.get("mch_id")
                   + "&product_id=" + map.get("product_id")
                   + "&time_stamp=" + map.get("time_stamp")
                   + "&nonce_str=" + map.get("nonce_str");
           return JsonUtil.ajaxReturn(str);
       }
   }
   
   

   测试该接口可以发现:wxPayConfigBean:null,显然即便这里用了@Autowired但还是注入失败了.然是如果我们通过junit直接测试:

   @Autowired
   public WxPayConfigBean wxPayConfigBean;
   
   @Test
   void contextLoads() {
       System.out.println(wxPayConfigBean.toString());
   }
   

   此时,数据注入又是成功的.

2. 查询了比较多的资料后我突然明白自己对于new和@Autuwired的理解还是有很大问题.new创建了一个新对象,但Autowired不是,它是通过先匹配类型再匹配名字的方式(这个顺序正好和@Resource相反)取出由spring管理的对象.回到上面的代码,可以发现在controller层我们拿到的WxPayServiceImpl对象是new出来的,而不是从spring管理的对象中取出的,那么WxPayServiceImpl中的wxPayConfigBean对象更不可能是spring中配置好的对象(相当于无参构造),所以导致最后输出为Null,只要稍微修改一下即可

   @RequestMapping("/payment")
   @RestController
   public class WxPayController {
   
       @Autowired
       public WxPayServiceImpl wxPayService;
   
       @RequestMapping("/wxpay/{product_id}")
       public String getWxQrCode(@PathVariable("product_id") Integer productId) {
           System.out.println(productId);
           return wxPayService.getWxQrCode(productId);
       }
   }