Remoting and web services using Spring[摘自官网]

spring document url:

http://docs.spring.io/spring/docs/

Using Hessian

First we’ll have to create a new servlet in your application (this is an excerpt from 'web.xml'):

<servlet>
    <servlet-name>remoting</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>remoting</servlet-name>
    <url-pattern>/remoting/*</url-pattern>
</servlet-mapping>

ou’re probably familiar with Spring’s DispatcherServlet principles and if so, you know that now you’ll have to create a Spring container configuration resource named 'remoting-servlet.xml' (after the name of your servlet) in the 'WEB-INF' directory.

Alternatively, consider the use of Spring’s simpler HttpRequestHandlerServlet. This allows you to embed the remote exporter definitions in your root application context (by default in 'WEB-INF/applicationContext.xml'), with individual servlet definitions pointing to specific exporter beans. Each servlet name needs to match the bean name of its target exporter in this case.

In the newly created application context called remoting-servlet.xml, we’ll create a HessianServiceExporter exporting your services:

<bean id="accountService" class="example.AccountServiceImpl">
    <!-- any additional properties, maybe a DAO? -->
</bean>

<bean name="/AccountService" class="org.springframework.remoting.caucho.HessianServiceExporter">
　　<!-- 构造需要的输入参数 -->
　　<property name="service" ref="accountService"/>
   <!-- 服务端客户端使用的接口 -->
   <property name="serviceInterface" value="example.AccountService"/>
</bean>

In the latter case, define a corresponding servlet for this exporter in 'web.xml', with the same end result: The exporter getting mapped to the request path/remoting/AccountService. Note that the servlet name needs to match the bean name of the target exporter.

<servlet>
    <servlet-name>accountExporter</servlet-name>
    <servlet-class>org.springframework.web.context.support.HttpRequestHandlerServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>accountExporter</servlet-name>
    <url-pattern>/remoting/AccountService</url-pattern>
</servlet-mapping>

to link in the service on the client, we’ll create a separate Spring container, containing the simple object and the service linking configuration bits:

<bean class="example.SimpleObject">
    <property name="accountService" ref="accountService"/>
</bean>

<bean id="accountService" class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
    <property name="serviceUrl" value="http://remotehost:8080/remoting/AccountService"/>
    <property name="serviceInterface" value="example.AccountService"/>
</bean>

//假设不定义SimpleObject
//配置文件名为spring-config-client.xml
//client可以使用这样的代码调用
ApplicationContext context = new ClassPathXmlApplicationContext("spring-config-client.xml");
AccountService accountService = (AccountService)context.getBean("accountService");

//
//POJO for transport
//
public class Account implements Serializable{

    private String name;

    public String getName(){
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}
//
//server and client
//
public interface AccountService {

    public void insertAccount(Account account);

    public List<Account> getAccounts(String name);

}
//
//server
// the implementation doing nothing at the moment
public class AccountServiceImpl implements AccountService {

    public void insertAccount(Account acc) {
        // do something...
    }

    public List<Account> getAccounts(String name) {
        // do something...
    }

}
//
//client
//
public class SimpleObject {

    private AccountService accountService;

    public void setAccountService(AccountService accountService) {
        this.accountService = accountService;
    }

    // additional methods using the accountService

}

org.springframework.remoting.caucho.HessianServiceExporter - This exports the specified service as a servlet based http request handler. Hessian services exported by this class can be accessed by any hessian client.
org.springframework.remoting.caucho.HessianProxyFactoryBean - This is the factory bean for Hessian clients. The exposed service is configured as a spring bean. The ServiceUrl property specifies the URL of the service and the ServiceInterface property specifies the interface of the implemented service.

1.Client sends a message call
2.This message call is handled by a Hessian Proxy created by HessianProxyFactoryBean
3.The Hessian Proxy converts the call into a remote call over HTTP
4.The Hessian Service Adapter created by HessianServiceExporter intercepts the remote call over HTTP
5.It forwards the method call to Service