1. Install the express framework globally, CMD open the command line, and enter the following command:
npm install -g express
In the express 4.x version, the command tool is separated, a command tool is installed, and the command is executed:
npm install -g express-generator
type express --version
2. If execute js file report error: Error: Cannot find module express
Solution:
execute it again under your own project directory:
npm install express
Project issues
An error was encountered in the Vue project today. The console reported error Component name “xxx“ should always be multi-word vue/multi-word-comp, which is mainly the error reported by eslint standardization
Solution:
Turn off naming rule verification
find it in the root directory eslintrc.js file, add the following code:
"vue/multi-word-component-names":"off",
.eslintrc.js file content:
Problems encountered during ROS learning:
Gazebo has been installed when ROS is installed. Use the following command to check whether the installation is successful, and open the gazebo simulation environment.
roslaunch gazebo_ros empty_world.launch
When opening gazebo in ROS for the first time, error will be report: Err] [REST.cc:205] Error in REST request
As shown in the figure below:
Solution:
It needs to be modified .ignition/fuel/config.yaml file
Open yaml file command:
sudo gedit ~/.ignition/fuel/config.yaml
Use # to comment out this code: url: https://api.ignitionfuel.org
Then add
url: https://api.ignitionrobotics.org
As shown in the following figure:
run the launch command again, and you will not see the above error warning.
roslaunch gazebo_ros empty_world.launchAn execution error occurred after installing GCC An error occurred while loading the C file
gcc: error trying to exec 'cc1': execvp: No such file or directory
After adding environment variables
whereis cc1
Find out where CC1 is
/usr/libexec/gcc/x86_64-redhat-linux/4.8.2/cc1
Position of CC1 in my centos7
If you can’t find it
locate cc1
Once found, copy
/usr/libexec/gcc/x86_64-redhat-linux/4.8.2
then
PATH="$PATH":/usr/libexec/gcc/x86_64-redhat-linux/4.8.2
Import environment variables
export PATH
That’s it
int max =std::numeric_limits< int>: max();
:: Based on error indicating:
f:\code\cpp\webspider\main. cpp(47): warning C4003: not enough actual parameters for macro ‘max’
f:\code\cpp\webspider\main. cpp(47) : error C2589: ‘(‘ : illegal token on right side of ‘::’
f:\code\cpp\webspider\main. cpp(47) : error C2059: syntax error : ‘::’
Cause: STL’s numeric_limits::max() and VC6 min/max macro conflict.
The problem should be that the macro definitions of the above two header files conflict.
Solution: Use parentheses “()” to avoid precompiler errors. int max = (std::numeric_limits<std::streamsize>::max)(); That’s it.
Problem description
When running code. The following error is reported:
"D:\Program Files\Java\jdk1.8.0_301\bin\java.exe" -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:54797,suspend=y,server=n -javaagent:C:\Users\Administrator\AppData\Local\JetBrains\IntelliJIdea2020.3\captureAgent\debugger-agent.jar -Dfile.encoding=UTF-8 -classpath "D:\program files\Java\jdk1.8.0_301\jre\lib\charsets.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\deploy.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\access-bridge-64.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\cldrdata.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\dnsns.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\jaccess.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\jfxrt.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\localedata.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\nashorn.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\sunec.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\sunjce_provider.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\sunmscapi.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\sunpkcs11.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\ext\zipfs.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\javaws.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\jce.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\jfr.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\jfxswt.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\jsse.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\management-agent.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\plugin.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\resources.jar;D:\program files\Java\jdk1.8.0_301\jre\lib\rt.jar;E:\JetBrains\spring学习\spring-study\spring-study-01-ioc1\target\test-classes;E:\JetBrains\spring学习\spring-study\spring-study-01-ioc1\target\classes;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-webmvc\5.3.10\spring-webmvc-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-aop\5.3.10\spring-aop-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-beans\5.3.10\spring-beans-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-context\5.3.10\spring-context-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-core\5.3.10\spring-core-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-jcl\5.3.10\spring-jcl-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-expression\5.3.10\spring-expression-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\springframework\spring-web\5.3.10\spring-web-5.3.10.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\junit\junit\4.13\junit-4.13.jar;D:\java\maven-3.8.1-bin\apache-maven-3.8.1\maven_repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;D:\program files\JetBrains\IntelliJ IDEA 2020.3.4\lib\idea_rt.jar" java.MyTest01
Connected to the target VM, address: '127.0.0.1:54797', transport: 'socket'
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.SecurityException: Prohibited package name: java
at java.lang.ClassLoader.preDefineClass(ClassLoader.java:655)
at java.lang.ClassLoader.defineClass(ClassLoader.java:754)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:601)
Disconnected from the target VM, address: '127.0.0.1:54797', transport: 'socket'
Process finished with exit code 1
Cause analysis:
Through the analysis of the error, I learned that I wrote that the use of java package’s name is prohibited in Java
Solution:
Delete and modify the name of java package to other
Demand
It is expected to dynamically render page components through array objects
method
Use the render method to create a component based on the type field of the object through $createElement and pass other parameters into the component
renderParent($h,parent) {
const values = this.values
const field = parent.options.field
let value ;
if(field){
value = values[field]
}
return $h(parent.type,{
props:{options:parent.options,value:value},on:{'change:value':(val) => {this.update(field,val)}}
},parent.children ?parent.children
.map(child => {
if(typeof child === 'string') return child
if(child.type){
return this.renderParent($h,child)
}
}) : ""
)
},
result
The following error is reported:
solve
When creating a component through ceateelement, add attrs attribute in the second parameter
Problem description
Recently, when backing up MySQL data, an error was found in dump database:
mysqldump: Got error: 1556: "You can't use locks with log tables." when using LOCK TABLES
Solution steps:
Checked because there are two table locks in the dump MySQL library.
Add --lock-tables =0 after mysqldump instruction.
Summary
Mysqldump backup will turn on the lock table by default – opt is turned on by default, which will affect the online business when backing up big data
To prevent this, we can use --skip-opt to cancel this default option in backup After adding this parameter, the above error report will not appear.
mysqldump --skip-opt -h<host> -u<user> -p<password> -A >> backup.sql --Perform full backups
I recently processed some large files of biological data. After writing the code, I found that the code was a bit wrong and needed to be modified, so I terminated the operation. However, since this process should take a long time to run and suddenly terminated, R will clear the archive. the error will be report:
Solution: use the following command to generate temporary Archive
dir.create(tempdir())I tried to restart it, but it seems to restart will not work.
After redirecting the command line output to the UI interface in the previous article, an error will be reported when closing the UI interface
Has no attribute of flush in Python or
PyQt: RuntimeError: wrapped C/C++ object has been deleted
The solution is to add a function in the class to which the command line output is redirected:
class ButtonOne(QThread):
_signalForText = pyqtSignal(str)
def __init__(self):
super(ButtonOne, self).__init__()
def write(self, text):
self.signalForText.emit(text)
def run(self):
for i in range(15):
time.sleep(1)
print(i)
print('end')
@property
def signalForText(self):
return self._signalForText
def flush(self):
passThis can be solved.
The added functions are:
def flush(self):
passFor errors:
CMake Error at D:\VSA_paper\VSA\CMakeLists.txt:48 (target_link_libraries): 1> [CMake] Cannot specify link libraries for target “variational” which is not built by this project.
All the information found said target_link_libraries is not placed behind add_executable, but not mine
the following is the code segment where the error is located
add_executable(${PROJECT_NAME}_bin ${SRCFILES} ${HEAD_FILES} ${RCC_FILES} ${WRAP_FILES} "gauss.h" "developable_degree.h")
target_link_libraries(${PROJECT_NAME} Qt5::Widgets Qt5::Core Qt5::Gui)
target_link_libraries(${PROJECT_NAME}_bin igl::core igl::opengl_glfw)
target_link_libraries(${PROJECT_NAME}_bin OpenMesh)
From the error “Cannot specify link libraries for target “variational” which is not built by this project.” You can see that the project name “variant” is wrong and should be “variant_bin”.
The solution is to add the missing “_bin” after ${project_name} in the above code segment. The modified result is as follows:
add_executable(${PROJECT_NAME}_bin ${SRCFILES} ${HEAD_FILES} ${RCC_FILES} ${WRAP_FILES} "gauss.h" "developable_degree.h")
#add Qt5
target_link_libraries(${PROJECT_NAME}_bin Qt5::Widgets Qt5::Core Qt5::Gui)
target_link_libraries(${PROJECT_NAME}_bin igl::core igl::opengl_glfw)
target_link_libraries(${PROJECT_NAME}_bin OpenMesh)
Problem description
The following error occurred while connecting Hikari. Initialization failed
ERROR 27468 — [nio-8080-exec-1] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 – Exception during pool initialization.
Cause analysis:
It may be a driving problem
The MySQL version on this machine is higher than the driver version used. Unable to connect. You can check the version of MySQL and compare it with the driver used. Then look at dependency import.
Solution:
My solution is as follows: because my MySQL version is 8.0, then I use the connection package of 5. So the connection failed. So I first import the 8.0 connection package, and then modify the dependent version number. Note: if you use the 8.0 connection package, you need to change the class forname to: com.mysql.cj.jdbc.Driver. Then the problem was solved