Class loading process
- The following diagram depicts the entire process from class loading into the JVM to unloading out of memory.
[Class loading life cycle]
It is divided into five steps: load, connect, initialize, use and uninstall.
- Load: Finds and loads the binaries of a class
- Connection: Merges binary files that have been read into memory into JVM China
- Validation: To ensure the correctness of the classes being loaded
- Preparation: Allocates memory for static variables of the class and initializes them
- Parse: Convert symbolic references in the constant pool to direct references
- Assign initial values to static variables of the class
function
- Loads the binaries of a class with its fully qualified name
- Converts the binaries of a class into a runtime data structure for the method area
- Create a java.lang.Class object on the heap that encapsulates the Class’s data structure in the method area and provides an interface.
Loading way
- The most common way: load from the local system, archive JAR files
- Dynamic loading: Compile Java source files into class files
- Other methods: Load files from network or proprietary databases
Class loader
- BootstrapClassLoader: Loads the BootstrapClassLoader base module classes
- PlatformClassLoader: Loads platform-specific classes
- AppClassLoader: Loads some application-level modules
- Custom class loader (UserClassLoader) : Users can customize the loading method of classes
Class loader relationships
[Class loading relationship]