Author Archives: Robins

[Solved] Springboot Error: org.apache.catalina.core.ContainerBase : A child container failed during start

Review springboot idea errors:

2021-09-08 21:12:43.851 ERROR 3704 --- [  restartedMain] org.apache.catalina.core.ContainerBase   : A child container failed during start

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: A child container failed during start
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[na:1.8.0_74]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:926) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:263) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardService.startInternal(StandardService.java:432) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:927) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.startup.Tomcat.start(Tomcat.java:486) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:123) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:104) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:450) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:199) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:182) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:160) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:577) [spring-context-5.3.9.jar:5.3.9]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:434) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:338) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1332) [spring-boot-2.5.4.jar:2.5.4]
	at com.sc.myapp.Application.main(Application.java:12) [classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_74]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_74]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_74]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_74]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.0.4.RELEASE.jar:2.0.4.RELEASE]
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:938) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:835) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1396) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1386) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_74]
	at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:919) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 26 common frames omitted
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[na:1.8.0_74]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:926) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 34 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
	at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:440) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1396) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1386) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_74]
	at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:919) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 34 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/tomcat/util/descriptor/tld/TldParser
	at org.apache.jasper.servlet.TldScanner.<init>(TldScanner.java:84) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.jasper.servlet.JasperInitializer.newTldScanner(JasperInitializer.java:100) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.jasper.servlet.JasperInitializer.onStartup(JasperInitializer.java:81) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5219) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.52.jar:9.0.52]
	... 40 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.tomcat.util.descriptor.tld.TldParser
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_74]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_74]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_74]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_74]
	... 45 common frames omitted

2021-09-08 21:12:43.851  INFO 3704 --- [  restartedMain] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-09-08 21:12:43.855  WARN 3704 --- [  restartedMain] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
2021-09-08 21:12:43.860  INFO 3704 --- [  restartedMain] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-09-08 21:12:43.873 ERROR 3704 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:163) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:577) ~[spring-context-5.3.9.jar:5.3.9]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:434) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:338) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343) [spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1332) [spring-boot-2.5.4.jar:2.5.4]
	at com.sc.myapp.Application.main(Application.java:12) [classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_74]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_74]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_74]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_74]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.0.4.RELEASE.jar:2.0.4.RELEASE]
Caused by: org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
	at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:142) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:104) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:450) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:199) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:182) ~[spring-boot-2.5.4.jar:2.5.4]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:160) ~[spring-boot-2.5.4.jar:2.5.4]
	... 13 common frames omitted
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:938) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:263) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardService.startInternal(StandardService.java:432) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:927) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.startup.Tomcat.start(Tomcat.java:486) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:123) ~[spring-boot-2.5.4.jar:2.5.4]
	... 18 common frames omitted
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: A child container failed during start
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[na:1.8.0_74]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:926) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 26 common frames omitted
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:938) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:835) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1396) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1386) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_74]
	at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:919) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 26 common frames omitted
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[na:1.8.0_74]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:926) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 34 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
	at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:440) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1396) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1386) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_74]
	at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_74]
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:919) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 34 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/tomcat/util/descriptor/tld/TldParser
	at org.apache.jasper.servlet.TldScanner.<init>(TldScanner.java:84) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.jasper.servlet.JasperInitializer.newTldScanner(JasperInitializer.java:100) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.jasper.servlet.JasperInitializer.onStartup(JasperInitializer.java:81) ~[tomcat-embed-jasper-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5219) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	... 40 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.tomcat.util.descriptor.tld.TldParser
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_74]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_74]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_74]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_74]
	... 45 common frames omitted

Solution: remove version

I guess it comes with a conflict with the version we imported

But add:

<!-- add the supportion to jsp files -->
		<dependency>
			<groupId>org.apache.tomcat</groupId>
			<artifactId>tomcat-jsp-api</artifactId>
		</dependency>

Otherwise, an error will be reported

There is no error when compiling and packaging the IDEA code, but the code displays an error

Uploading… Re-upload cancel

The figure is casually found on the Internet. It shows that the code is compiled successfully, but the packaging fails. When maven reimprot and mavn clean and idea invalidate cache are useless, it is recommended to empty the. Idea and. IML files in the workspace folder
the reason is incomplete or incorrect package guide information, which is caused by the disordered configuration information of the workspace of the idea itself.

 . iml Folder

Idea means module configuration information. Information of module
IML is the project configuration file of IntelliJ idea, which contains some configuration information of the current project Idea stores the configuration information of the project, including history, version control information, etc.

 .idea Folder

Idea stores the configuration information of the project, including history, version control information, etc.

Mybatisenumtypehandler upgrade error of mybatis plus

Background

After I recently upgraded mybatis plus from 3.4.1 to 3.4.3.1, a series of errors occurred. The first error is that an attribute of the configuration file is red:

Prompt that there is a problem with the path of mybatisenumtypehandler. It is true that this class does not exist in the source package

Solution

Later, I queried the whole project by copying this type, and finally found this class. It turned out that it was moved to other places, and it can be moved to other packages at will. It’s too casual!

Original address:

default-enum-type-handler: com.baomidou.mybatisplus.extension.handlers.MybatisEnumTypeHandler

New address:

default-enum-type-handler: com.baomidou.mybatisplus.core.handlers.MybatisEnumTypeHandler

After modification, it will not be popular and solve the problem.

There is also an error:

A setusedeprecetedexecutor attribute in config became popular. It turned out that a plug-in was removed in the new version. You need to configure the latest version of paging plug-in

Screenshot of error reporting:

Solution:

Configure the latest version of paging plug-in on the official website:

Official website link: https://mp.baomidou.com/guide/page.html

Latest configuration:

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
        return interceptor;
    }

SpringBoot+Swagger Error: 403 Forbidden [How to Solve]

Springboot + swagger2 reports error 403 Forbidden

Error reporting reason

When creating a springboot project, if spring security dependencies are introduced into the POM file, after spring boot starter security, springboot will enable authentication by default, and also enable CSRF (Cross Site Request Forgery Prevention) verification by default. Therefore, the post request will be intercepted, that is, an error 403 Forbidden will be reported, and the get request will not be intercepted

Solution

Use ignore to ignore interception and manually turn off CSRF protection. Remember to turn on annotation @ enablewebsecurity manually

@EnableWebSecurity
public class WebSecurityCongfig extends WebSecurityConfigurerAdapter {

    @Override
    public void configure(WebSecurity web) throws Exception {
        web.ignoring().antMatchers("/**");
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.cors().and().csrf().disable();
    }
}

How to Solve Opencv Reads Video Error: cv2.error

Recently, due to the needs of the project, I often need to use OpenCV to read video. I often encounter a problem that an error will be reported after reading the video. Although it does not affect the code results, I really can’t stand being picky.

Error reporting procedures:

# -*-coding:utf-8-*-
"""
File Name: read_video.py
Program IDE: PyCharm
Create File By Author: Hong
"""
import cv2


def read_video(video_path: str):
    """
    OpenCV read video widget, solve the video read error problem
    :param video_path: input the path of the video file to be read
    :return: no return value
    """
    print('Video path:', video_path)
    cap = cv2.VideoCapture(video_path)
    while cap.isOpened():
        # get a frame
        ret, frame = cap.read()

        cv2.imshow("capture", frame)

        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    print('Read through the video!')
    cap.release()
    cv2.destroyAllWindows()


if __name__ == '__main__':
    path = r'D:\multi_insect_videos\multi_object00.mp4'
    read_video(path)

You can read the video normally, but the result will output an error

Traceback (most recent call last):
  File "E:/PyCharmDocument/create_ST_image/multi_insect_processing/crop_video_to_images.py", line 76, in <module>
    read_video(path)
  File "E:/PyCharmDocument/create_ST_image/multi_insect_processing/crop_video_to_images.py", line 65, in read_video
    cv2.imshow("capture", frame)
cv2.error: OpenCV(4.5.3) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-uzca7qz1\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

The reason is that after the video is finished, the imshow() function of OpenCV can’t read the frame and makes an error. Solution: add judgment before imshow(). Read-only when there are frames. Exit the loop directly when there are no frames.

Error-free code:

# -*-coding:utf-8-*-
"""
File Name: read_video.py
Program IDE: PyCharm
Create File By Author: Hong
"""
import cv2


def read_video(video_path: str):
    """
    OpenCV read video widget, solve the video read error problem
    :param video_path: input the path of the video file to be read
    :return: no return value
    """
    print('Video path:', video_path)
    cap = cv2.VideoCapture(video_path)
    while cap.isOpened():
        # get a frame
        ret, frame = cap.read()
        if not ret:
            break
        cv2.imshow("capture", frame)

        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    print('Read through the video!')
    cap.release()
    cv2.destroyAllWindows()


if __name__ == '__main__':
    path = r'D:\multi_insect_videos\multi_object00.mp4'
    read_video(path)

Program output results:

Video path: D:\multi_insect_videos\multi_object00.mp4
Read through the video!

Process finished with exit code 0

[Solved] Kafka Error: InvalidReplicationFactorException: Replication factor:

Error:
InvalidReplicationFactorException: Replication factor:
1 larger than available brokers
The reason is that the configuration in kafka’s zk doesn’t match the creation parameters

Solution:
Open server.properties
vim /opt/module/kafka/config/server.properties
View Configuration
zookeeper.connect=hadoop102:2181,hadoop103:2181,hadoop104:2181/kafka
Create a topic at this time
bin/kafka-topics.sh –zookeeper hadoop102:2181/kafka –create –replication-factor 3 –partitions 1 –topic first
Here the zookeeper parameter value must be the same as the configured one

Comparison method violates its general contract [How to Solve]

Error code:

//Error Codes
        Comparator<InspectReportListItemMpVo> comparator = new Comparator<InspectReportListItemMpVo>() {
            @Override
            public int compare(InspectReportListItemMpVo o1, InspectReportListItemMpVo o2) {
                try {
                    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                    Date reportTime_o1 = simpleDateFormat.parse(o1.getReportTime());
                    Date reportTime_o2 = simpleDateFormat.parse(o2.getReportTime());
//                    return reportTime_o1.compareTo(reportTime_o2);
                    return reportTime_o2.compareTo(reportTime_o1);
                } catch (ParseException e) {
                    e.printStackTrace();
                    return 1;
                }
            }
        };
        result.getItems().sort(comparator);

Screenshot of error reporting:

Comparison method violates its general contract

Problem-solving:

(not rigorous!) return 1 in the catch block; Change to return 0;

Supplement: rigorous writing

       Collections.sort(list, new Comparator<String>() {
            public int compare(String arg1, String arg2) {
                /**
                 * Modified
                 */
                if(StringUtils.isBlank(arg1) ) {
                    if(StringUtils.isBlank(arg2)) {
                        return 0;
                    }else {
                        return -1;
                    }
                    
                }else if(StringUtils.isBlank(arg2)){
                    return 1;
                }
                
                return arg1.compareTo(arg2);
            }
        });

Cause: timsort has a reflexivity check

Timport algorithm rules:
after JDK7, after implementing the comparable interface, the following three characteristics should be met:
1) Reflexivity: the comparison results of X and y are opposite to those of Y and X
2) transitivity: X > y,y> z. Then x > z。
3) symmetry: if x = y, the comparison results of X and Z are the same as those of Y and Z.

For the above error code, if you directly return 1, assume that a is empty, a.compareto (b) = 1, and b.compareto (a) = 1, which does not satisfy reflexivity

[Solved] Python 3.7 from collections import Iterable Error

Python 3.7 use from collections import Iterable error

Error Message:
DeprecationWarning: Using or importing the ABCs from ‘collections’ instead of from ‘collections.abc’ is deprecated, and in 3.8 it will stop working
from collections import Iterable

Solution:
Change to from collections.abc import Iterable

Gazebo Error: Error in REST request [How to Solve]

Error log

Gazebo[Err][REST.cc:205] Error in REST request

Problem-solving

nano ~/.ignition/fuel/config.yaml
# Modify url: https://api.ignitionrobotics.org

[Solved] XFire Error: org.codehaus.xfire.fault.XFireFault

When the client calls, the following errors are found in the package:

rg.codehaus.xfire.fault.XFireFault: There must be a method name element.
at org.codehaus.xfire.service.binding.RPCBinding.readMessage(RPCBinding.java:36)

There is a problem with the URL in the client code. Just remove ?wsdl

That is to say:

String url = "http://localhost:8080/xfire/services/AdvancedService?wsdl";

Amend to read:

String url = "http://localhost:8080/xfire/services/AdvancedService";

It’s OK.

Tomcat service startup error: cannot allocate memory [How to Solve]

Today, an environment hung up. First, restart it. It was found that it didn’t get up. The following error was reported:

....
Cannot allocate memory

1. Check whether the thread is full first:
# check the maximum allowed processes

[root@test ~] sysctl kernel.pid_max
kernel.pid_max = 32768

#View the number of processes in progress on this server

[root@test ~] ps -eLf | wc -l
1597

2. Compare the above two values. If the two values are similar, increase the number of allowed processes:
Modify PID_ Max value (custom)

[root@test ~] echo 999999 > /proc/sys/kernel/pid_max

Settings take effect permanently

[root@test ~] echo "kernel.pid_max=999999" >> /etc/sysctl.conf
[root@test ~] sysctl -p

3. If it is not, check the Tomcat log:

then modify the memory allocation:

1. [root@test ~] vim/etc/sysctl.conf 
vm.overcommit_memory=1
   [root@test ~] sysctl -p  

2.[root@test ~] echo 1 > /proc/sys/vm/overcommit_memory
  [root@test ~] sysctl –p  

3. [root@test ~] sysctl  vm.overcommit_memory=1

Explanation:
memory allocation strategy in the kernel: overcommit_Memory
optional values: 0, 1, 2

0,: indicates that the kernel will check whether there is enough available memory for the process to use; If there is enough available memory, the memory application is allowed; Otherwise, the memory request fails and the error is returned to the application process
1: indicates that the kernel is allowed to allocate all physical memory regardless of the current memory state
2: indicates that the kernel allows to allocate more memory than the sum of all physical memory and swap space.

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