扫描Class文件的方法

看了别人的代码多了,总能够学习一些东西的,把自己学的东西都点滴都记录下来.

今天自己以前写的一个简单的工具包,用来扫描类,可以扫描jar文件和包里的文件,说明如下:

1.扫描是某子类的Class,可以是包及其子包下的Class包括jar文件里的Class
2.扫描类上含有某(可以是多个)注解的Class,可以是包及其子包下的Class包括jar文件里的Class

直接贴部分代码吧:

还有其他依赖的类,由于篇幅原因就不贴出来了,下面说说怎么使用吧

public class ResolverUtil<T> {
  /*
   * An instance of Log to use for logging in this class.
   */
  private static final Logger log = LoggerFactory.getLogger(ResolverUtil.class);

  /**
   * A simple interface that specifies how to test classes to determine if they
   * are to be included in the results produced by the ResolverUtil.
   */
  public static interface Test {
    /**
     * Will be called repeatedly with candidate classes. Must return True if a class
     * is to be included in the results, false otherwise.
     */
    boolean matches(Class<?> type);
  }

  /**
   * A Test that checks to see if each class is assignable to the provided class. Note
   * that this test will match the parent type itself if it is presented for matching.
   */
  public static class IsA implements Test {
    private Class<?> parent;

    /** Constructs an IsA test using the supplied Class as the parent class/interface. */
    public IsA(Class<?> parentType) {
      this.parent = parentType;
    }

    /** Returns true if type is assignable to the parent type supplied in the constructor. */
    public boolean matches(Class<?> type) {
      return type != null && parent.isAssignableFrom(type);
    }

    @Override
    public String toString() {
      return "is assignable to " + parent.getSimpleName();
    }
  }

  /**
   * A Test that checks to see if each class is annotated with a specific annotation. If it
   * is, then the test returns true, otherwise false.
   */
  public static class AnnotatedWith implements Test {
    private Class<? extends Annotation> annotation;

    /** Constructs an AnnotatedWith test for the specified annotation type. */
    public AnnotatedWith(Class<? extends Annotation> annotation) {
      this.annotation = annotation;
    }

    /** Returns true if the type is annotated with the class provided to the constructor. */
    public boolean matches(Class<?> type) {
      return type != null && type.isAnnotationPresent(annotation);
    }

    @Override
    public String toString() {
      return "annotated with @" + annotation.getSimpleName();
    }
  }

  /** The set of matches being accumulated. */
  private Set<Class<? extends T>> matches = new HashSet<Class<? extends T>>();

  /**
   * The ClassLoader to use when looking for classes. If null then the ClassLoader returned
   * by Thread.currentThread().getContextClassLoader() will be used.
   */
  private ClassLoader classloader;

  /**
   * Provides access to the classes discovered so far. If no calls have been made to
   * any of the {@code find()} methods, this set will be empty.
   *
   * @return the set of classes that have been discovered.
   */
  public Set<Class<? extends T>> getClasses() {
    return matches;
  }

  public ClassLoader getClassLoader() {
    return classloader == null ? Thread.currentThread().getContextClassLoader() : classloader;
  }

  public void setClassLoader(ClassLoader classloader) {
    this.classloader = classloader;
  }

  public ResolverUtil<T> findImplementations(Class<?> parent, String... packageNames) {
    if (packageNames == null)
      return this;

    Test test = new IsA(parent);
    for (String pkg : packageNames) {
      find(test, pkg);
    }

    return this;
  }


  public ResolverUtil<T> findAnnotated(Class<? extends Annotation> annotation, String... packageNames) {
    if (packageNames == null)
      return this;

    Test test = new AnnotatedWith(annotation);
    for (String pkg : packageNames) {
      find(test, pkg);
    }

    return this;
  }

  public ResolverUtil<T> find(Test test, String packageName) {
    String path = getPackagePath(packageName);

    try {
      List<String> children = VFS.getInstance().list(path);
      for (String child : children) {
        if (child.endsWith(".class"))
          addIfMatching(test, child);
      }
    } catch (IOException ioe) {
      log.error("Could not read package: " + packageName, ioe);
    }

    return this;
  }

 
  public ResolverUtil<T> find(String packageName, Test test) {
	  return find(test, packageName);
  }
  
  public ResolverUtil<T> find(String packageName, Test ...test) {
    String path = getPackagePath(packageName);

    try {
      List<String> children = VFS.getInstance().list(path);
      for (String child : children) {
        if (child.endsWith(".class"))
          addIfMatching(child, test);
      }
    } catch (IOException ioe) {
      log.error("Could not read package: " + packageName, ioe);
    }

    return this;
  }
  
 
  protected String getPackagePath(String packageName) {
    return packageName == null ? null : packageName.replace('.', '/');
  }

  @SuppressWarnings("unchecked")
  protected void addIfMatching(Test test, String fqn) {
    try {
      String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
      ClassLoader loader = getClassLoader();
      log.debug("Checking to see if class " + externalName + " matches criteria [" + test + "]");

      Class<?> type = loader.loadClass(externalName);
      if (test.matches(type)) {
        matches.add((Class<T>) type);
      }
    } catch (Throwable t) {
      log.warn("Could not examine class '" + fqn + "'" + " due to a " +
          t.getClass().getName() + " with message: " + t.getMessage());
    }
  }
  
  @SuppressWarnings("unchecked")
  protected void addIfMatching( String fqn, Test ...test) {
	  try {
		  String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
		  ClassLoader loader = getClassLoader();
		  log.debug("Checking to see if class " + externalName + " matches criteria [" + test + "]");
		  
		  Class<?> type = loader.loadClass(externalName);
		  boolean flag = false;
		  for (int i = 0; i < test.length; i++) {
			  if (test[i].matches(type)) {
				  flag = true;
				  break;
			  }
		  }
		  if(flag){
			  matches.add((Class<T>) type);
		  }
	  } catch (Throwable t) {
		  log.warn("Could not examine class '" + fqn + "'" + " due to a " +
				  t.getClass().getName() + " with message: " + t.getMessage());
	  }
  }
}

public static void main(String[] args) {
		Set<Class<? extends Class<?>>> typeSet = null;
		ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
		
		//1.扫描org下的类Class,包括jar包里的Class
		resolverUtil.find(new ResolverUtil.IsA(Object.class), "org.slf4j");
		typeSet = resolverUtil.getClasses();
		System.out.println(typeSet);
		
		//2.以单个个注解方式扫描Class
		resolverUtil.findAnnotated(javax.annotation.Resource.class, "org.mdc");
		typeSet = resolverUtil.getClasses();
		System.out.println(typeSet);
		
		//3.以多个注解方式扫描Class
		resolverUtil.find("org.mdc", new ResolverUtil.AnnotatedWith(javax.annotation.Resource.class), new ResolverUtil.AnnotatedWith(javax.xml.ws.WebFault.class));
		typeSet = resolverUtil.getClasses();
		System.out.println(typeSet);
		
		
	}