Comment processing of scannotation and Java libraries
Comment processing of scannotation and Java libraries
Overview:
In Java development, annotations are a metadata form that is used to add additional description information to class, methods, fields, etc.In the Java class library, it is often necessary to handle annotations to achieve some specific functions.Scannotation is a Java class library that is used to scan and process annotations in the class files quickly and simply.
Use of scannotation:
Scannotation finds and handle the annotation by scanning by class path.The following is the step of using scannotation:
1. Introduce the scannotation library: Add the jar file of the Scannotation library to the project's classpath.
2. Create an annotation processor: Create a class to process the annotation. This class needs to inherit the AnnotationVisitor interface and implement the method.AnnotionVisitor provides a method of accessing the annotation, which can obtain information such as the elemental value of the annotation.
3. Execute scanning: scanning and processing the annotation information in class files by scanning and processing by scanning function provided by Scannotation.The following is a simple example code:
import org.scannotation.ClasspathUrlFinder;
import org.scannotation.AnnotationDB;
import org.scannotation.ClasspathUrlResolver;
public class AnnotationProcessor {
public static void main(String[] args) throws Exception {
// Set the class path scanner
ClasspathUrlResolver resolver = new ClasspathUrlResolver();
ClasspathUrlFinder.setClassLoader(Thread.currentThread().getContextClassLoader());
ClasspathUrlFinder.setHttp(ClasspathUrlFinder.findWebInfClassesPath());
// Create an annotation processor
AnnotationProcessor visitor = new AnnotationProcessor();
// Create AnnotationDB object
AnnotationDB db = new AnnotationDB();
db.setScanClassAnnotations(true);
db.setScanMethodAnnotations(false);
db.setScanFieldAnnotations(false);
// Execute scanning
db.scanArchives(resolver.resolve("", ""));
// Get the scanning result
for (String className : db.getAnnotationIndex().get("com.example.MyAnnotation")) {
System.out.println(className);
}
}
}
In the above example, we first set up a class path scanner and then created the annotation processor.Next, we created an AnnotationDB object and set the types of annotations that need to be scanned.Finally, we execute the scan by calling the Scanarchives method and obtaining the scanning results through the getannotationIndex method.
Features of scannotation:
Scannotation has the following characteristics:
1. Quick scanning: Scannotation uses some optimization techniques to make the scanning speed very fast.
2. Simple use: Use Scannotation can simplify the annotation processing process to reduce the workload and error opportunities of developers.
3. Multi -function: Scannotation can not only scan the annotations in the class file, but also support scanning other types of files, such as XML, JSP, etc.
Summarize:
Scannotation is a class library for scanning and processing the annotations in the Java file.By using Scannotation, we can quickly and easily handle the annotations to achieve some specific functions.In Java development, annotation processing is a very important technology. Through the use of the Scannotation class library, we can improve development efficiency and code quality.
Please note that the above examples are only used to demonstrate the basic usage of Scannotation. In actual use, appropriate modification and expansion may need to be appropriately modified according to specific needs.
