J2OBJC Annotations Framework in Java Library User Guide

The J2OBJC annotation framework retains specific annotation information when converting Java code to Objective-C code.These annotations can guide the conversion process by using annotations in the Java library to ensure that the generated Objective-C code is consistent with the source code.This article will introduce how to correctly use the J2OBJC annotation framework in the Java library and provide some example code. 1. Introduce the J2OBJC annotation framework library First, you need to introduce the library of the J2OBJC annotation framework in the Java project.This operation can be completed by adding corresponding dependencies in Maven or Gradle to build a file to ensure that the required frame library is included in the construction process. 2. Use annotations in the Java library Once you introduce the library of the J2OBJC annotation framework, you can start using annotations in the Java library to guide the conversion process.Here are some commonly used J2OBJC annotations and its usage: -`@Weak`: The object that needs to be marked with this annotation to keep it with weak reference after the conversion.In Java, weak references are implemented through the `Weakreference`.For example: @Weak private Object weakObject; -`@RetAINED`: Use this annotation to mark the object that needs to be referenced after the conversion.In Java, a strong reference is a default reference type to ensure that the object will not be recovered by garbage when it is no longer referenced.For example: @Retained private Object retainedObject; -`@Mapping`: Use this annotation to define the name or method name of the conversion Objective-C.For example: @Mapping("CustomClass") public class MyClass { @Mapping("customMethod") public void myMethod() { // ... } } -`@native`: Methods or fields to mark the Objective-C code after the converting use.For example: public class NativeClass { @Native("nativeMethodName") public native void myNativeMethod(); } -`@Deprecated`: use the annotation to mark outdated classes, methods, or fields as abandoned.In this way, in the conversion Objective-C code, developers will see the corresponding prompts.For example: @Deprecated public class DeprecatedClass { // ... } 3. Configuration conversion option In addition to using annotations in the Java library, you can also configure the option for the J2OBJC conversion process.These options include the folder of the conversion output, the path stored in the header file, whether the annotation is retained during the conversion process.These options can be set by adding corresponding configuration items in Maven or Gradle to build files. For example, in Maven's `pom.xml` file, you can add the following configuration to define the storage path of the output folder and header file: <build> <plugins> ... <plugin> <groupId>com.google.j2objc</groupId> <artifactId>j2objc-maven-plugin</artifactId> <version>1.4</version> <executions> <execution> <goals> <goal>j2objc</goal> </goals> </execution> </executions> <configuration> <outputDirectory>src/main/objc</outputDirectory> <headerMappingsDirectory>src/main/objc</headerMappingsDirectory> </configuration> </plugin> ... </plugins> </build> 4. Execute conversion After completing the above steps, you can execute the J2OBJC conversion process and convert the Java code into Objective-C code.This operation can be performed through the corresponding commands of Maven or Gradle.After the conversion is complete, you will get the corresponding Objective-C code file in the specified output folder. The above is the use of J2OBJC annotation framework in the Java library.By using J2OBJC annotations, you can instruct the conversion process to ensure that the generated Objective-C code is consistent with the source code.I hope the information provided in this article will help you!