Here are some of the tidying up I just came into contact with ：
- Tomcat The role of each directory is simple to sort out ：
- bin： Directory of execution files , The general execution file is placed inside （ such as startup.bat 、 startup.sh file ）
- conf： Profile directory ,Tomcat Profile directory
- lib： Store all kinds of things you need jar Package directory
- logs： Log file directory
- temp： It's in the catalog Tomcat Temporary files generated during operation , Be careful , Files in the directory can be deleted , however temp The catalogue must not be deleted , Prone to unknown errors .
- webapps： General installation packages accessed through browsers are unzipped in this directory ,bin The runtime will call the files in this directory .
- work：work Directory some people call it cache directory , But it's not very accurate ,work It's actually Tomcat Working directory of , Namely Tomcat hold jsp Turn it into class The working directory of the file . The compiled files will be cached in this directory ,Tomcat The directory displayed will be from work Look in the catalog jsp The compiled class file , If the directory is empty , This process will be repeated , For example, sometimes the modified page is in Tomcat It can't be displayed in operation , May be work There's a cache inside , Delete work After the corresponding file inside , restart Tomcat Will come out . notes ：work Files in the directory can be deleted , however work The directory cannot be deleted , It's prone to unforeseen errors
2. General Tomcat Indistinguishes Windows and Linux, because Tomcat Of bin There are two forms of executable files in the directory , A kind of .bat The file in Windows Run under , A kind of .sh The file in Linux Run under .
3.Java distinguish Windows and Linux edition , however Java It can be used across platforms , because Java The compiled code is not run directly by the hardware system , It's a kind of middle code （ Bytecode ）, Then different hardware platforms have different JVM（Java virtual machine）, Then from JVM Translate the intermediate code into the code that can be executed by the corresponding hardware system . So different hardware systems have JVM,Java It can be used across platforms .
4.Java It is divided into JDK（Java development kit） and JRE（Java runtime environment）,JRE Namely Java Running environment , If you just run Java If it's a program, it just needs JRE, But it needs to be compiled Java You need to JDK,JDK Contained in the JRE.
5.Redis Hot standby and cold standby ：
Hot standby ： It's running in a database , Backup data in the form of archive
Cold standby ： It's when the database has been shut down normally , Copy the database file to another location .
6. environment variable ： Environmental variables are equivalent to the field of vision of the system , The environment variables are configured in the system's view , If there is no configuration, it will not be in the field of vision of the system . If the environment variable is configured, the corresponding program can be found in the system , If there is no configuration, you can't find . In simple terms, you can't configure variables in the software environment .（ another , When configuring environment variables, if there is already a variable name , You just need to add a semicolon after the variable value of the variable ‘;’ Distinguish it from the value of the variable added later ） notes ： If you modify environment variables , Make sure you remember to back it up ~ ~