ReflectionsJava 运行时元数据分析
Reflections 通过扫描 classpath，索引元数据，允许在运行时查询这些元数据，也可以保存收集项目中多个模块的元数据信息。
使用 Reflections 可以查询以下元数据信息：
1）获得某个类型的所有子类型
2）获得标记了某个注解的所有类型／成员变量，支持注解参数匹配。
3）使用正则表达式获得所有匹配的资源文件
4）获得所有特定签名（包括参数，参数注解，返回值）的方法
Reflections 依赖 Google 的 Guava 库和 Javassist 库。
Maven 项目导入
<dependency> <groupId>org.reflections</groupId> <artifactId>reflections</artifactId> <version>0.9.10</version> </dependency>
通常用法：
Reflections reflections = new Reflections("my.project");
Set<Class<? extends SomeType>> subTypes = reflections.getSubTypesOf(SomeType.class);
Set<Class<?>> annotated = reflections.getTypesAnnotatedWith(SomeAnnotation.class);
Reflections 初始化代码。
//scan urls that contain 'my.package', include inputs starting with 'my.package', use the default scanners
Reflections reflections = new Reflections("my.package");
//or using ConfigurationBuilder
new Reflections(new ConfigurationBuilder()
.setUrls(ClasspathHelper.forPackage("my.project.prefix"))
.setScanners(new SubTypesScanner(),
new TypeAnnotationsScanner().filterResultsBy(optionalFilter), ...),
.filterInputsBy(new FilterBuilder().includePackage("my.project.prefix"))
...);
以下是一些使用例子代码。
//SubTypesScanner Set<Class<? extends Module>> modules = reflections.getSubTypesOf(com.google.inject.Module.class);
//TypeAnnotationsScanner Set<Class<?>> singletons = reflections.getTypesAnnotatedWith(javax.inject.Singleton.class);
//ResourcesScanner
Set<String> properties =
reflections.getResources(Pattern.compile(".*\\.properties"));
//MethodAnnotationsScanner Set<Method> resources = reflections.getMethodsAnnotatedWith(javax.ws.rs.Path.class); Set<Constructor> injectables = reflections.getConstructorsAnnotatedWith(javax.inject.Inject.class);
//FieldAnnotationsScanner Set<Field> ids = reflections.getFieldsAnnotatedWith(javax.persistence.Id.class);
//MethodParameterScanner Set<Method> someMethods = reflections.getMethodsMatchParams(long.class, int.class); Set<Method> voidMethods = reflections.getMethodsReturn(void.class); Set<Method> pathParamMethods = reflections.getMethodsWithAnyParamAnnotated(PathParam.class);
//MethodParameterNamesScanner List<String> parameterNames = reflections.getMethodParamNames(Method.class)
//MemberUsageScanner Set<Member> usages = reflections.getMethodUsages(Method.class)
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