Java 获取所有子类信息

时间:2024-10-14 10:05:26

我以前的博客(Java Scala获取注解的类信息)介绍过通过Reflections工具通过使用特定注解的类的信息,其实本工具也可以获取接口,抽象类,类等的所有子类信息。使用方法如下:

Reflections reflections = new Reflections("my.project");
Set<Class<? extends SomeType>> subTypes = reflections.getSubTypesOf(SomeType.class);

下面实例来说明如何使用的:

定义接口:

package test.reflection;

/**
* 类功能描述://TODO
*
* @author WangXueXing create at 19-5-4 下午10:16
* @version 1.0.0
*/
public interface Base {
void doSomeThing();
}

定义子类1:

package test.reflection;

/**
* 类功能描述://TODO
*
* @author WangXueXing create at 19-5-4 下午10:18
* @version 1.0.0
*/
public class SubClass1 implements Base{
@Override
public void doSomeThing() {
System.out.println("SubClass1");
}
}

定义子类2:

package test.reflection;

/**
* 类功能描述://TODO
*
* @author WangXueXing create at 19-5-4 下午10:18
* @version 1.0.0
*/
public class SubClass2 implements Base{
@Override
public void doSomeThing() {
System.out.println("SubClass2");
}
}

测试获取所有Base的子类信息:

package test.reflection;

import org.reflections.Reflections;

import java.util.Set;

/**
* 类功能描述://TODO
*
* @author WangXueXing create at 19-5-4 下午10:19
* @version 1.0.0
*/
public class Test {
public static void main(String[] args){
Reflections reflections = new Reflections("test.reflection");
Set<Class<? extends Base>> subTypes = reflections.getSubTypesOf(Base.class);
subTypes.forEach(x -> System.out.println(x));
}
}

结果输出如下:

class test.reflection.SubClass1
class test.reflection.SubClass2

如上如何获取所有子类信息。

其实Reflections还有其他很有用的功能,如下了解下:

一. Reflections的其他用法

使用默认的scanners,浏览url包含my.package的路径,包括以my.package开头的

Reflections reflections = new Reflections("my.package");

使用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"))
...);

然后方便的使用查询方法,这要根据具体scanners配置
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)

如果没有配置scanner,默认使用SubTypesScannerTypeAnnotationsScanner
也可以配置Classloader,用来解析某些实时类
保证能够解析到url
git上的例子:https://github.com/ronmamo/reflections/tree/master/src/test/java/org/reflections

三. ReflectionUtils

ReflectionsUtils包含了一些方便的方法,形式类似*getAllXXX(type, withYYY)
比如

import static org.reflections.ReflectionUtils.*;

Set<Method> getters = getAllMethods(someClass,
withModifier(Modifier.PUBLIC), withPrefix("get"), withParametersCount(0)); //or
Set<Method> listMethodsFromCollectionToBoolean =
getAllMethods(List.class,
withParametersAssignableTo(Collection.class), withReturnType(boolean.class)); Set<Fields> fields = getAllFields(SomeClass.class, withAnnotation(annotation), withTypeAssignableTo(type));

四. ClasspathHelper

获取包、class、classloader的方法
使用maven可以很方便的集成到项目中,可以把浏览的元数据存储到xml/json文件中,下一次不必浏览,直接使用
在maven中,使用Reflections Maven plugin插件
其他用法

  • 并行查找url
  • 序列化查找为xml/json
  • 直接利用存储的元数据,快速load,不必再次scan
  • 存储模型实体为.java文件,可以通过静态方式引用types/fields/methods/annotation
  • 初始化srping的包浏览

五. 注解的例子

获取包中,带TaskOption注解的类,然后获取注解的task()

    Map<Class<? extends Task>, Class<?>> optionMap = new HashMap<>();
for (Class<?> clazz : reflections.getTypesAnnotatedWith(TaskOption.class)) {
TaskOption taskOption = clazz.getAnnotation(TaskOption.class);
if (taskOption == null) continue; // this shouldn't happen
optionMap.put(taskOption.task(), clazz);
}

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