Http Invoker

Http Invoker使用HTTP傳送物件，傳送時使用Java的序列化機制來傳送，由於透過HTTP傳送，所以在使用它們時要搭配Spring Web框架來使用，也就是使用到DispatcherServlet，可以改寫 Hessian、Burlap，只要修改一下service-config.xml就可以了：

service-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" 
 "http://www.springframework.org/dtd/spring-beans.dtd"> 

<beans>   
    <bean id="urlMapping" 
          class="org.springframework.web.servlet.
                   → handler.SimpleUrlHandlerMapping"> 
        <property name="mappings"> 
            <props> 
                <prop key="/some.service">serviceExporter</prop> 
            </props> 
        </property> 
    </bean> 
    
    <bean id="viewResolver" 
          class="org.springframework.web.servlet.
                   → view.InternalResourceViewResolver"> 
        <property name="prefix"> 
            <value>/WEB-INF/jsp/</value> 
        </property> 
        <property name="suffix"> 
            <value>.jsp</value> 
        </property> 
    </bean> 

    <bean id="someService" 
          class="onlyfun.caterpillar.SomeServiceImpl"/>

    <bean id="serviceExporter" 
          class="org.springframework.remoting.
                   → httpinvoker.HttpInvokerServiceExporter">
        <property name="service">
            <ref bean="someService"/>
        </property>
        <property name="serviceInterface">
            <value>onlyfun.caterpillar.ISomeService</value>
        </property>        
    </bean>
</beans>

接下來客戶端的部份，可以改寫 Hessian、Burlap 的內容，修改一下Bean定義檔的內容：

invoker-client.xml

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" 
  "http://www.springframework.org/dtd/spring-beans.dtd"> 

<beans> 
    <bean id="someServiceProxy" 
          class="org.springframework.remoting.
                     → httpinvoker.HttpInvokerProxyFactoryBean">
        <property name="serviceUrl">
            <value>
            http://localhost:8080/HttpInvokerDemo/some.service
            </value>
        </property>
        <property name="serviceInterface">
            <value>onlyfun.caterpillar.ISomeService</value>
        </property>
    </bean>
</beans>

注意到"serviceUrl"屬性的設定，它是個標準的HTTP請求位址，來撰寫個簡單的客戶端程式以使用Http Invoker伺服器上的服務：

HessianClient.java

package onlyfun.caterpillar;

import org.springframework.context.ApplicationContext;
import org.springframework.context.
              support.FileSystemXmlApplicationContext;

public class HessianClient {
    public static void main(String[] args) {
        ApplicationContext context =
            new FileSystemXmlApplicationContext(
                    "invoker-client.xml");

        ISomeService service = 
            (ISomeService) context.getBean("someServiceProxy");

        String result1 = service.doSomeService("Some request");
        System.out.println(result1);

        int result2 = service.doOtherService(1);
        System.out.println(result2);
    }
}

執行的結果與 RMI 是相同的。