[解决方案] spring-mvc 400错误解决办法

先让我们看一下错误信息

HTTP Status 400 -
type Status report

message

description The request sent by the client was syntactically incorrect.

Apache Tomcat/7.0.47

---

@PathVariable 导致400的错误代码

/**
 * @author lvgo
 * @version 1.0
 * @Description: 调试400错误
 * @date 2018/1/17 14:44
 */
@Controller
public class ItemController {

    Logger log = Logger.getLogger(ItemController.class);

    @Autowired
    private ItemService itemService;

    @RequestMapping("/item/{itemId}")
    @ResponseBody
    public TbItem getItemById(@PathVariable Long id) {
        TbItem tbItem = itemService.findById(id);
        return tbItem;
    }
} 

简单看一下上面代码觉得似乎没有什么不对的地方,但是启动之后访问 /item/param 就会报 400 错误

---

修改后代码

/**
 * @author lvgo
 * @version 1.0
 * @Description: 调试400错误
 * @date 2018/1/17 14:44
 */
@Controller
public class ItemController {

    Logger log = Logger.getLogger(ItemController.class);

    @Autowired
    private ItemService itemService;

    //错误写法
    @RequestMapping("/item/{itemId}")
    @ResponseBody
    public TbItem getItemById(@PathVariable Long id) {
        TbItem tbItem = itemService.findById(id);
        return tbItem;
    }

    // 如果使用了@PathVariable注解就一定要遵守注解规则
    // 方法参数要么与路径参数相同,要么自定义value值为路径的对应值

    // 正确写法1
    @RequestMapping("/item/{itemId}")
    @ResponseBody
    public TbItem getItemById(@PathVariable(value="itemId") Long id) {
        TbItem tbItem = itemService.findById(id);
        return tbItem;
    }

    // 正确写法2
    @RequestMapping("/item/{itemId}")
    @ResponseBody
    public TbItem getItemById(@PathVariable Long itemId) {
        TbItem tbItem = itemService.findById(itemId);
        return tbItem;
    }


}

@RequestParam 导致400的正确写法

 /**
 * @author lvgo
 * @version 1.0
 * @Description: 调试400错误
 * @date 2018/1/17 14:44
 */
@Controller
public class ItemController {

    Logger log = Logger.getLogger(ItemController.class);

    @Autowired
    private ItemService itemService;

    // 1.参数必须要传入 name = id
    @RequestMapping("/item")
    @ResponseBody
    public TbItem getItemById(@RequestParam Long id) {
        TbItem tbItem = itemService.findById(id);
        return tbItem;
    }

    // 2.这样参数就必须要是 name = itId
    @RequestMapping("/item")
    @ResponseBody
    public TbItem getItemById(@RequestParam(value = "itId") Long id) {
        TbItem tbItem = itemService.findById(id);
        return tbItem;
    }

    // 3.这样是给了参数的默认值
    @RequestMapping("/item")
    @ResponseBody
    public TbItem getItemById(@RequestParam(value = "itId",default = "0") Long id) {
        TbItem tbItem = itemService.findById(itemId);
        return tbItem;
    }


}