Java 它有一个;“春天之路”;从带注释的接口获取实现?
我想扔掉一些样板。假设我有一个带有自定义注释的自定义接口:Java 它有一个;“春天之路”;从带注释的接口获取实现?,java,spring,interface,annotations,spring-aop,Java,Spring,Interface,Annotations,Spring Aop,我想扔掉一些样板。假设我有一个带有自定义注释的自定义接口: interface MyInterface { @DoSomething("crazy") public String aMethod(int numberOfJumps); } 现在我可以编写一个InvocationHandler,并生成一个Proxy实现,它根据注释和方法参数执行一些或多或少有用的操作,并返回一个适当的结果。这个很好用 我的问题是,我是否可以使用Spring的一些机制来获得相同的结果,但可能更安全
interface MyInterface {
@DoSomething("crazy")
public String aMethod(int numberOfJumps);
}
现在我可以编写一个InvocationHandler
,并生成一个Proxy
实现,它根据注释和方法参数执行一些或多或少有用的操作,并返回一个适当的结果。这个很好用
我的问题是,我是否可以使用Spring的一些机制来获得相同的结果,但可能更安全、更快、更灵活和/或更可配置。SpringAOP注释看起来很有希望,但它们似乎需要一个类,而不是一个接口
[更新]
为了明确我在这里想要的是我当前代码的概要:
public interface TestInterface {
@MyAnnotation(name = "foo")
public void testMethod(String arg);
}
public class AnnotationProxy {
@SuppressWarnings("unchecked")
public static <T> T getImplementation(Class<T> annotatedInterface) {
return (T) Proxy.newProxyInstance(annotatedInterface.getClassLoader(),
new Class<?>[]{annotatedInterface},
new AnnotationHandler());
}
private static class AnnotationHandler implements InvocationHandler {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("Args " + Arrays.toString(args));
System.out.println("Annotations" + Arrays.toString(method.getAnnotations()));
return "useful value";
}
}
}
TestInterface ti = getImplementation(TestInterface.class);
String s = ti.testMethod("xyz"); //"useful value"
公共接口测试界面{
@MyAnnotation(name=“foo”)
公共void testMethod(字符串arg);
}
公共类注释代理{
@抑制警告(“未选中”)
公共静态GetT实现(类annotatedInterface){
return(T)Proxy.newProxyInstance(annotatedInterface.getClassLoader(),
新类[]{annotatedInterface},
新的AnnotationHandler());
}
私有静态类AnnotationHandler实现InvocationHandler{
公共对象调用(对象代理、方法、对象[]args)抛出Throwable{
System.out.println(“Args”+Arrays.toString(Args));
System.out.println(“Annotations”+Arrays.toString(method.getAnnotations());
返回“有用值”;
}
}
}
TestInterface ti=getImplementation(TestInterface.class);
字符串s=ti.testMethod(“xyz”)//“有用价值”
如你所见,我用稀薄的空气创建了一个对象(还有一些丑陋的反射)。我想知道我是否可以用一种更文明、更像spring的方式来实现这一点。您可以使用spring AOP来拦截和后期处理带注释的方法:
@Aspect
public class ProcessDoSomethingAspect {
@AfterReturning(value = "execution(@annotation(doSomething) * *.*(..))", returning = "result")
public String processResult(my.package.DoSomething doSomething, String result) {
// process result here
return result;
}
}
一种方法是扫描具有您喜欢的注释方法的接口,在Spring应用程序上下文中创建并注册代理 示例 让我们有一个接口
Test
,我们要为其创建并注册代理:
package com.test;
public interface Test {
@DoSomething(pattern = "[%s]")
void print(String value);
}
我们的注释如下所示:
package com.test;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface DoSomething {
String pattern();
}
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.test.Test;
public class Main {
public static void main(final String[] args) throws Exception {
final ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("test.xml");
final Test test = ctx.getBean(Test.class);
test.print("Hello");
}
}
我们希望在这样的应用程序中使用它:
package com.test;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface DoSomething {
String pattern();
}
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.test.Test;
public class Main {
public static void main(final String[] args) throws Exception {
final ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("test.xml");
final Test test = ctx.getBean(Test.class);
test.print("Hello");
}
}
我们的test.xml Spring配置文件只包含组件扫描:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.1.xsd">
<context:component-scan base-package="com.test"/>
</beans>
不中肯。为了创建和注册代理,我们必须实现扫描接口和创建代理:
package com.test;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Map;
import java.util.Set;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.core.io.Resource;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.MethodMetadata;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.SimpleMetadataReaderFactory;
import org.springframework.stereotype.Component;
@Component
public class DoSomethingPostprocessor implements BeanFactoryPostProcessor, ApplicationContextAware {
private ApplicationContext applicationContext;
private Object createDoSomethingBean(final MethodMetadata mmd, final Map<String, Object> attributes)
throws Exception {
final String pattern = (String) attributes.get("pattern");
final Class<?> clazz = Class.forName(mmd.getDeclaringClassName());
return Proxy.newProxyInstance(clazz.getClassLoader(), new Class[] { clazz },
new InvocationHandler() {
@Override
public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
System.out.println(String.format(pattern, args[0]));
return null;
}
});
}
@Override
public void postProcessBeanFactory(final ConfigurableListableBeanFactory beanFactory) throws BeansException {
try {
final String packageSearchPath = "classpath*:com/**/*.class";
final Resource[] resources =
applicationContext.getResources(packageSearchPath);
final SimpleMetadataReaderFactory factory = new
SimpleMetadataReaderFactory(applicationContext);
for (final Resource resource : resources) {
final MetadataReader mdReader = factory.getMetadataReader(resource);
final AnnotationMetadata am = mdReader.getAnnotationMetadata();
final Set<MethodMetadata> methodMetadata =
am.getAnnotatedMethods(DoSomething.class.getName());
for (final MethodMetadata mmd : methodMetadata) {
final Map<String, Object> attributes =
mmd.getAnnotationAttributes(DoSomething.class.getName());
final String beanName = mmd.getDeclaringClassName();
beanFactory.registerSingleton(beanName, createDoSomethingBean(mmd, attributes));
}
}
} catch (final Exception e) {
throw new RuntimeException(e);
}
}
@Override
public void setApplicationContext(final ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
package.com.test;
导入java.lang.reflect.InvocationHandler;
导入java.lang.reflect.Method;
导入java.lang.reflect.Proxy;
导入java.util.Map;
导入java.util.Set;
导入org.springframework.beans.BeansException;
导入org.springframework.beans.factory.config.BeanFactoryPostProcessor;
导入org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
导入org.springframework.context.ApplicationContext;
导入org.springframework.context.ApplicationContextAware;
导入org.springframework.core.io.Resource;
导入org.springframework.core.type.AnnotationMetadata;
导入org.springframework.core.type.MethodMetadata;
导入org.springframework.core.type.classreading.MetadataReader;
导入org.springframework.core.type.classreading.SimpleMetadataReaderFactory;
导入org.springframework.stereotype.Component;
@组成部分
公共类DoSomethingPostprocessor实现BeanFactoryPostProcessor,ApplicationContextAware{
私有应用程序上下文应用程序上下文;
私有对象createDoSomethingBean(最终方法元数据mmd,最终映射属性)
抛出异常{
final String pattern=(String)attributes.get(“pattern”);
最终类clazz=Class.forName(mmd.getDeclaringClassName());
返回Proxy.newProxyInstance(clazz.getClassLoader(),新类[]{clazz},
新的调用处理程序(){
@凌驾
公共对象调用(最终对象代理、最终方法、最终对象[]args)抛出Throwable{
System.out.println(String.format(pattern,args[0]);
返回null;
}
});
}
@凌驾
public void后处理beanFactory(最终可配置的ListableBeanFactory beanFactory)引发BeanException{
试一试{
最终字符串包searchpath=“classpath*:com/***/*.class”;
最终资源[]资源=
获取资源(packageSearchPath);
最终SimpleMetadataReaderFactory工厂=新建
SimpleMetadataReaderFactory(applicationContext);
for(最终资源:资源){
final MetadataReader mdReader=factory.getMetadataReader(资源);
final AnnotationMetadata am=mdReader.getAnnotationMetadata();
最终设置方法元数据=
am.getAnnotatedMethods(DoSomething.class.getName());
对于(最终MethodMetadata mmd:MethodMetadata){
最终地图属性=
mmd.getAnnotationAttributes(DoSomething.class.getName());
最后一个字符串beanName=mmd.getDeclaringClassName();
registerSingleton(beanName,createDoSomethingBean(mmd,attributes));
}
}
}捕获(最终异常e){
抛出新的运行时异常(e);
}
}
@凌驾
public void setApplicationContext(最终ApplicationContext ApplicationContext)引发BeansException{
this.applicationContext=applicationContext;
}
}
不确定,但您可以将spring aop的xml方法用于接口方法。我不确定使用带注释的接口是否是一种好的做法,例如,当使用CGLIB代理时,我相信有关接口方法的信息