Some mistakes that Xiaobai often makes (update from time to time, and promise not to make them again next time)

Some mistakes Xiaobai often makes （ Update from time to time , Promise not to do it again ）

Preface ：

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This is an error correction article , Record all kinds of codes of Xiaobai at ordinary times debug daily , Xiaobai once encountered these bug, It took a lot of time , In order not to make low-level mistakes , Write this article specially .
If you like, you can like the collection , Level co., LTD. , Welcome to error correction .

problem 1：SpringBoot Project startup failed ！

Error message ：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'eduCommentController': Unsatisfied dependency expressed through field 'uCenterClient'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.atguigu.eduservice.client.UCenterClient': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: No fallback instance of type class com.atguigu.eduservice.client.impl.UCenterClientImpl found for feign client service-ucenter

Error type ：

org.springframework.beans.factory.UnsatisfiedDependencyException
reason ：
Not in the Feign Add... To the implementation class of the remote call class @Service annotation , As a result, this class is not added Spring Containers , initialization failed ！

Solution ：
Add @Service annotation

problem 2： Front page 404

Error message ：


Error type ：
Failed to load resource: the server responded with a status of 500 (NuxtServerError)
NuxtServerError
Request failed with status code 404
reason ：
Appear this kind of 404 Errors are generally 2 One reason , Or the back-end code is missing , Or the address of the previous call is written incorrectly .
I am here api The calling address is wrong

Solution ：

	// According to instructor ID Inquire about lecturer information and courses 
    getTeacherInfo(teacherId){
    
        return request({
    
            url: '/eduservice/front/teacher/getTeacherInfo/' + teacherId,
            method: 'get'
        })
    }

problem 3：org.springframework.web.HttpRequestMethodNotSupportedException: Request method ‘GET’ not supported

Error message ：
Back end ：
org.springframework.web.HttpRequestMethodNotSupportedException: Request method ‘GET’ not supported
front end ：

Uncaught (in promise) Error: Network Error
    at createError (createError.js?2d83:16)
    at XMLHttpRequest.handleError (xhr.js?b50d:83)

Error type ：
org.springframework.web.HttpRequestMethodNotSupportedException
reason ：
There is no error in the back-end interface , There is an error in the request mode when calling the front end

Solution ：
take get The request was changed to post request

	// Paging query 
    getTeacherPage(page,limit){
    
        return request({
    
            url: `/eduservice/front/teacher/getTeacherPage/${
      page}/${
      limit}`,
            method: 'post'
        })
    },

problem 4： Paging query does not return data

Error message ：

Back end ：
There was no error at first , But will http://localhost:9001/eduservice/front/course/getCoursePage/1/8 After copying the manual request, an error is found

java.lang.NullPointerException
	at com.atguigu.eduservice.service.impl.EduCourseServiceImpl.getCourseFrontPage(EduCourseServiceImpl.java:169)

front end ：

You can see that the front end failed to call the back-end interface , Copy the middle post Submission found that the back end reported a null pointer exception

Error type ：
java.lang.NullPointerException
reason ：

You can find . The method for get Submit , But there's a @RequestBody Annotated parameters ,@RequestBody Comments need to be passed in json data , obviously get What cannot be done when submitting , Need to change to post Submit .

Solution ：
It is amended as follows post Submit

	// Conditional query with paging query course 
    @PostMapping("/getCoursePage/{page}/{limit}")
    @ApiOperation(" Conditional query with paging query course ")
    public R getCoursePage(@PathVariable long page, @PathVariable long limit,
                           @RequestBody(required = false) CourseDetailVo courseDetailVo){
    

        Page<EduCourse> coursePage = new Page<>(page, limit);

        Map<String,Object> map = courseService.getCourseFrontPage(coursePage, courseDetailVo);

        return R.ok().data(map);
    }

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debug daily , Update from time to time ...