Detailed explanation of the "SHIMS" framework implementation principle in the Java class library
The "SHIMS" framework in the Java class library is a technology used to achieve compatibility.It allows the old version of the Java code to be compatible with the new version of the Java class library and can still run on the new version of the Java platform.This article will introduce the implementation principle of the "SHIMS" framework in detail and provide the corresponding Java code example.
In the Java ecosystem, with the development and improvement of the Java platform, the interfaces and functions of the class library often change.When we upgrade the version of the Java platform, we may encounter the problem that the old code cannot be compatible with the new version of the library.This is because the old version of the code may use a class, method or interface that has been abandoned or removed.To solve this problem, the "SHIMS" framework came into being.
The implementation of the implementation of the "shims" framework is as follows:
1. Library version detection: First, the application will detect the version of the currently run Java library.You can obtain the version number of the java runtime by using the `System.getProperty (" Java.Version ") method.
2. Dynamic loading: According to the current library version, the application dynamically loads the corresponding version of the "SHIM" class.
3. Implementation of the "Shim" class: Each "SHIM" class is a adapter. It implements a compatible interface between the old and the new version of the library, and uses the new version of the library to achieve these interfaces.
4. Forward call: Once the "Shim" class is loaded, it will become the middle layer between the old version code and the new version of the library.When the old version of the code calls the "shim" class, the method will forward the corresponding method of calling the new version library.
Below is a simple example, demonstrating how to use the "SHIMS" framework to implement the class library compatibility:
// Old version interface
public interface OldLibraryInterface {
void oldMethod();
}
// Old version category
public class OldLibrary implements OldLibraryInterface {
@Override
public void oldMethod() {
System.out.println("This is the old method implementation.");
}
}
// New version interface
public interface NewLibraryInterface {
void newMethod();
}
// New version category
public class NewLibrary implements NewLibraryInterface {
@Override
public void newMethod() {
System.out.println("This is the new method implementation.");
}
}
// "shim" adapter
public class LibraryShim implements OldLibraryInterface {
private NewLibraryInterface newLibrary;
public LibraryShim() {
newLibrary = new NewLibrary();
}
@Override
public void oldMethod() {
newLibrary.newMethod();
}
}
// app
public class Application {
public static void main(String[] args) {
OldLibraryInterface library;
// Select the right implementation according to the class library version
if (isOldLibraryVersion()) {
library = new OldLibrary();
} else {
library = new LibraryShim();
}
// Call compatibility method
library.oldMethod();
}
private static boolean isOldLibraryVersion() {
// Get the version number of java runtime
String javaVersion = System.getProperty("java.version");
// Judging whether it is the old version
return javaVersion.startsWith("1.8");
}
}
In the above example, the application selects the appropriate implementation based on the results returned by the method of `isoldlibrationVering ()`.If it is an old version, the old version of the library is implemented directly; if it is a new version, use the "Shim" adapter to forward the method of calling the new version of the library.In this way, whether it is the old version of the code or the new version code, it can be run on different versions of the Java library and is compatible.
In summary, the "SHIMS" framework is dynamically loaded with the adapter class, and the new version of the library is used to achieve the interface or method of the old versions, and the compatibility of different versions of the Java class library is achieved.This provides us with greater flexibility and maintenance in the process of upgrading the Java platform.
