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C# 关键字 as is

爱做梦的夏夏 03-24 13:00 阅读 2
环境 java17 + springboot 3.x

如题,简单来说,jersey官方希望用户通过 register 的方式,将所有的资源类注册到jersey中,但是,一般开发中,可能定义了N个Resource类,一个一个的加入,太麻烦,也可能遗漏,解决方案就是,写个方法,扫描到resource包下的所有资源类,然后 register 到jersey中

特别注意,是 registerClasses 方法,不是 register 方法

以下两种方法

  1. 使用java自带的扫描
    1.1 核心代码
import lombok.extern.slf4j.Slf4j;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.util.ClassUtils;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

@Slf4j
public class ClassUtil {

    /**
     * 由于spring boot 打包为jar包,jersey packages 无法扫描jar对应的文件夹的文件,故自定义包扫描
     *
     * @return class[]
     */
    public static Set<Class<?>> findAllClasses(String... scanPackages) {
        Set<Class<?>> classes = new HashSet<>();
        for (String scanPackage : scanPackages) {
            ClassLoader loader = ClassUtil.class.getClassLoader();
            Resource[] resources = new Resource[0];
            try {
                resources = scan(loader, scanPackage);
            } catch (IOException e) {
                log.error("加载class异常", e);
            }
            classes.addAll(convert(loader, resources));
        }
        return classes;
    }

    /**
     * 扫描 jar 包
     *
     * @param loader      ClassLoader
     * @param packageName packageName
     */
    private static Resource[] scan(ClassLoader loader, String packageName) throws IOException {
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(loader);
        String pattern = "classpath*:" + ClassUtils.convertClassNameToResourcePath(packageName) + "/*.class";
        return resolver.getResources(pattern);
    }

    /**
     * 加载 class
     *
     * @param loader   ClassLoader
     * @param resource resource
     */
    private static Class<?> loadClass(ClassLoader loader, Resource resource) {
        try {
            CachingMetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(loader);
            MetadataReader reader = metadataReaderFactory.getMetadataReader(resource);
            return ClassUtils.forName(reader.getClassMetadata().getClassName(), loader);
        } catch (LinkageError | ClassNotFoundException e) {
            if (log.isDebugEnabled()) {
                log.debug("Ignoring candidate class resource " + resource + " due to " + e);
            }
            return null;
        } catch (Throwable e) {
            if (log.isWarnEnabled()) {
                log.warn("Unexpected failure when loading class resource " + resource, e);
            }
            return null;
        }
    }

    /**
     * resources 转换为 Set<Class>
     *
     * @param loader    ClassLoader
     * @param resources Resource
     */
    private static Set<Class<?>> convert(ClassLoader loader, Resource[] resources) {
        Set<Class<?>> classSet = new HashSet<>(resources.length);
        for (Resource resource : resources) {
            Class<?> clazz = loadClass(loader, resource);
            if (clazz != null) {
                classSet.add(clazz);
            }
        }
        return classSet;
    }

}
1.2 使用
@Configuration
public class JerseyConfig extends ResourceConfig {

    public JerseyConfig() {
        // 注册包扫描 这个方法在开发使用没问题,但是打包jar后,找不到 class 文件
//        packages("com.xxx.xxx.api");

        // 定义扫描包含接口资源包
        registerClasses(ClassUtil.findAllClasses("com.xxx.xxx.api"));
    }
}
  1. 使用JerseyScan
    2.1 核心代码
    注意中间的 scanner.addIncludeFilter(new AnnotationTypeFilter(Path.class)); 这一行代码!!!
public class JerseyServiceAutoScanner {
    private JerseyServiceAutoScanner() {}

    public static Class[] getPublishJerseyServiceClasses(ApplicationContext context, String... scanPackages) {
        // 传入applicationContext对象,在整个spring容器中捞我们需要的controller
        // 传入的第二个参数是可变参数,字符串,用于传入需要扫描的包路径
        List<Class> jerseyServiceClasses = new ArrayList<>();
        if (scanPackages == null || scanPackages.length == 0) {
            return jerseyServiceClasses.toArray(new Class[jerseyServiceClasses.size()]);
        }
        ClassPathScanningCandidateComponentProvider scanner = new JerseyScanningComponentProvider(false);
        // 我只需要扫描使用了@Path注解的controller,如果还有其他的组合条件,可以在这里增加
        scanner.addIncludeFilter(new AnnotationTypeFilter(Path.class));
        for (var scanPackage : scanPackages) {
            jerseyServiceClasses.addAll(scanner.findCandidateComponents(scanPackage).stream()
                    .map(beanDefinition -> ClassUtils
                            .resolveClassName(beanDefinition.getBeanClassName(), applicationContext.getClassLoader()))
                    .collect(Collectors.toSet()));
        }
        // 返回符合条件的spring容器中的全部的类对象
        return jerseyServiceClasses.toArray(new Class[jerseyServiceClasses.size()]);
    }

    private static class JerseyScanningComponentProvider extends ClassPathScanningCandidateComponentProvider {
        public JerseyScanningComponentProvider(boolean useDefaultFilters) {
            super(useDefaultFilters);
        }
        @Override
        protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
            AnnotationMetadata metadata = beanDefinition.getMetadata();
            // 注意这里的值,最好debug一下,我使用的时候,只有第一个metadata.isIndependent()是true
            return (metadata.isIndependent() && metadata.isAbstract() && !beanDefinition.getMetadata().isAnnotation());
        }
    }
}
2.2 引用
@Configuration
public class JerseyConfig extends ResourceConfig implements ApplicationContextAware {

    private ApplicationContext applicationContext;
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    @PostConstruct
    public void init() {
        registerClasses(JerseyServiceAutoScanner.getPublishJerseyServiceClasses(applicationContext, "com.xxx.xxx.api"));
    }
    public JerseyConfig() {
    // 。。。 其他的 。。。
    }
}

完结!!!

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