Hessian與spring集成

Hessian可以與spring完美無縫的集成，我們先來看一下如何集成：

• 服務(wù)端服務(wù)暴露

@Autowired
private HelloService helloService;

@Bean(name = "/helloService")
public HessianServiceExporter exportHelloService() {
    HessianServiceExporter exporter = new HessianServiceExporter();
    exporter.setService(helloService);
    exporter.setServiceInterface(HelloService .class);
    return exporter;
}

以上使用spring在代碼配置聲明bean的方式暴露了一個hession服務(wù)：http://localhost:8080/Hello/helloService

• 客戶端聲明與調(diào)用

聲明

<bean id="studentService" class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
        <!-- 請求代理Servlet路徑 -->
        <property name="serviceUrl">
            <value>http://localhost:8080/Hello/helloService</value>
        </property>
        <!-- 接口定義 -->
        <property name="serviceInterface">
            <value>com.test.hello.service.HelloService</value>
        </property>
</bean>

調(diào)用

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:/spring/ApplicationContext.xml");
HelloService helloService = (HelloService) context.getBean("helloService");
helloService.sayHi("hi, i am client");

存在的問題

上述的方法是最常用的集成方式，但存在一個問題，如果我們現(xiàn)在要在服務(wù)端暴露另外一個服務(wù)，那么需要添加如下代碼：

@Autowired
private AnotherService1 anotherService;

@Bean(name = "/anotherService")
public HessianServiceExporter exportAnotherService() {
    HessianServiceExporter exporter = new HessianServiceExporter();
    exporter.setService(anotherService);
    exporter.setServiceInterface(AnotherService .class);
    return exporter;
}

如果再來一個服務(wù)呢，那我們就再添加類似的代碼，能不能不重復(fù)添加這些類似的暴露代碼呢？

使用注解自動暴露服務(wù)

首先，新建一個叫HessianService的注解類，注意這個注解類包含了spring的Service注解

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.stereotype.Service;

@Target({ java.lang.annotation.ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Service
public @interface HessianService {
    public abstract String value() default "";
}

接著，我們把原先用@Service注解的服務(wù)類換成@HessianService

@HessianService
public class HelloServiceImpl implements HelloService {
    ...
    ...
}

然后，我們使用spring的BeanFactoryPostProcessor機制，動態(tài)暴露hessian服務(wù)

@Component
public class HessianServiceScanner implements BeanFactoryPostProcessor {

    public void postProcessBeanFactory(
            ConfigurableListableBeanFactory beanFactory) throws BeansException {
        String[] beanNames = beanFactory
                .getBeanNamesForAnnotation(HessianService.class);
        for (String beanName : beanNames) {
            String className = beanFactory.getBeanDefinition(beanName)
                    .getBeanClassName();
            Class<?> clasz = null;
            try {
                clasz = Class.forName(className);
            } catch (ClassNotFoundException e) {
                throw new BeanInitializationException(e.getMessage(), e);
            }
            String hessianServiceBeanName = "/" + beanName.replace("Impl", "");

            BeanDefinitionBuilder builder = BeanDefinitionBuilder
                    .rootBeanDefinition(HessianServiceExporter.class);
            builder.addPropertyReference("service", beanName);
            builder.addPropertyValue("serviceInterface",
                    clasz.getInterfaces()[0].getName());
            ((BeanDefinitionRegistry) beanFactory).registerBeanDefinition(
                    hessianServiceBeanName, builder.getBeanDefinition());
        }
    }

}