前言
上一篇文章Hessian入门体验与分析介绍了hessian的简单入门，并且从源码层面对Hessian的调用流程进行了分析；发现使用原生的Hessian还是比较繁琐的，下面看看Spring与Hessian进行整合并且进行简要分析。
使用
提供三个模拟块，分别模拟client，server以及被依赖的jar；对应的模块名称分别是：hessianClient，hessianServer以及hessianJar
1.hessianJar介绍
hessianJar主要提供被hessianClient和hessianServer依赖的公共类，这里主要提供了接口类IHessianService和pojo对象Bean
IHessianService类：
public interface IHessianService {
public String getString(String value);
public Bean getBean();
}对象Bean：
public class Bean implements Serializable {
private static final long serialVersionUID = 1L;
private String value;
public Bean(String value) {
this.value = value;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}2.hessianSever介绍
hessianServer主要用来对外提供服务的，因为hessian本身是基于http协议的，所以可以直接部署到web容器中比如tomcat，http协议解析可以直接交给web容器；此处因为将服务的发布交给Spring来处理，提供配置文件如下：
spring-server-hessian.xml：
<?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:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:lang="http://www.springframework.org/schema/lang"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
<bean id="hessionService" class="zh.hessian.hessianServer.HessianServiceImpl" />
<bean name="/hessianService.do"
class="org.springframework.remoting.caucho.HessianServiceExporter">
<property name="service" ref="hessionService" />
<property name="serviceInterface" value="zh.hessian.hessianJar.IHessianService" />
</bean>
</beans> web.xml：
<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
classpath:spring-hessian.xml
</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
</web-app>HessianServiceImpl：
public class HessianServiceImpl implements IHessianService {
@Override
public String getString() {
return "string";
}
@Override
public Bean getBean() {
return new Bean("value");
}
}3.hessianClient介绍
hessianClient模拟客户端的调用，对hessianSever发起请求，并且接受回复；此处因为将客户端的调用交给Spring来处理，提供配置文件如下：
spring-client-hessian.xml：
<?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"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<bean id="hessionServiceClient"
class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
<property name="serviceUrl"
value="http://localhost:8080/hessianServer/hessianService.do" />
<property name="serviceInterface" value="zh.hessian.hessianJar.IHessianService" />
</bean>
</beans> HessianSpringClient：
public class HessianSpringClient {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring-client-hessian.xml");
IHessianService service = (IHessianService) context.getBean("hessionServiceClient");
System.out.println(service.getString());
System.out.println(service.getBean().getValue());
}
}部署测试
运行结果如下：
getString:REQ + zhaohui
getBean:valueSpring整合Hessian调用分析
1.HessianProxyFactoryBean类
配置文件spring-client-hessian.xml中定义的对象class都是HessianProxyFactoryBean类，而我们通过上一篇文章中了解到Hessian通过在客户端使用动态代理的方式来实现RPC，HessianProxyFactoryBean代码如下：
public class HessianProxyFactoryBean extends HessianClientInterceptor implements FactoryBean<Object> {
private Object serviceProxy;
@Override
public void afterPropertiesSet() {
super.afterPropertiesSet();
this.serviceProxy = new ProxyFactory(getServiceInterface(), this).getProxy(getBeanClassLoader());
}
public Object getObject() {
return this.serviceProxy;
}
public Class<?> getObjectType() {
return getServiceInterface();
}
public boolean isSingleton() {
return true;
}
}发现HessianProxyFactoryBean实现了FactoryBean接口，而接口的方法getObject()正是我们在调用context.getBean(“x”)的时候被调用，所以获取的bean其实是serviceProxy，通过ProxyFactory的getProxy方法获取，具体代码如下：
public Object getProxy(ClassLoader classLoader) {
return createAopProxy().getProxy(classLoader);
}serviceProxy其实是通过AopProxy获取的代理类，AopProxy有两个实现类分别是：CglibAopProxy和JdkDynamicAopProxy，分别对应的两种动态代理方式，具体使用哪种，通过DefaultAopProxyFactory中如下代码来实现：
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config))
{
Class targetClass = config.getTargetClass();
if (targetClass == null) {
throw new AopConfigException("TargetSource cannot determine target class: " +
"Either an interface or a target is required for proxy creation.");
}
if (targetClass.isInterface()) {
return new JdkDynamicAopProxy(config);
}
return CglibProxyFactory.createCglibProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}这里使用的是JdkDynamicAopProxy，部分代码如下：
final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {
public Object getProxy(ClassLoader classLoader) {
if (logger.isDebugEnabled()) {
logger.debug("Creating JDK dynamic proxy: target source is " +
this.advised.getTargetSource());
}
Class[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised);
findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
......
Object retVal;
......
invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
retVal = invocation.proceed();
......
return retVal;
}
}JdkDynamicAopProxy实现了InvocationHandler接口，每次在调用方法(如：hessianService.getString(“zhaohui”))时，自动触发invoke方法；这里将需要的参数比如：(target,method,args等)封装到了ReflectiveMethodInvocation中，在ReflectiveMethodInvocation的proceed()方法中又调用了HessianProxyFactoryBean中的invoke()方法，部分代码如下：
public Object invoke(MethodInvocation invocation) throws Throwable {
if (this.hessianProxy == null) {
throw new IllegalStateException("HessianClientInterceptor is not properly initialized - " +
"invoke 'prepare' before attempting any operations");
}
ClassLoader originalClassLoader = overrideThreadContextClassLoader();
try {
return invocation.getMethod().invoke(this.hessianProxy, invocation.getArguments());
}
......
}其中最关注的是hessianProxy对象，这里通过反射的方式调用了hessianProxy对象里面的指定方法(比如：hessianService.getString(“zhaohui”))，hessianProxy对象在初始化HessianProxyFactoryBean的时候就初始化好了，具体代码如下：
protected Object createHessianProxy(HessianProxyFactory proxyFactory) throws MalformedURLException {
Assert.notNull(getServiceInterface(), "'serviceInterface' is required");
return proxyFactory.create(getServiceInterface(), getServiceUrl());
}这段代码有没有很熟悉，就是上一篇文章Hessian入门体验与分析中的客户端代码，如下所示：
String url = "http://localhost:8080/hessianServer-0.0.1-SNAPSHOT/hessianService";
HessianProxyFactory factory = new HessianProxyFactory();
IHessianService hessianService = null;
hessianService = (IHessianService) factory.create(IHessianService.class, url);这里的getServiceInterface()和getServiceUrl()正是我们在spring-client-hessian.xml为hessionServiceClient配置的两个属性，其实到这里下面的流程就和上一篇文章Hessian入门体验与分析中完全一样了。
2.代理类HessianProxy
具体分析同Hessian入门体验与分析
3.http请求类
具体分析同Hessian入门体验与分析
4.发送请求
具体分析同Hessian入门体验与分析
5.服务器端接受消息
web.xml中配置了处理消息的servlet:DispatcherServlet，在启动服务器并初始化DispatcherServlet的时候，加载了配置在spring-server-hessian.xml中的org.springframework.remoting.caucho.HessianServiceExporter；DispatcherServlet只是启动一个映射的作用，真正的处理在
HessianServiceExporter类中，部分代码如下：
public void invoke(InputStream inputStream, OutputStream outputStream) throws Throwable {
Assert.notNull(this.skeleton, "Hessian exporter has not been initialized");
doInvoke(this.skeleton, inputStream, outputStream);
}
protected void doInvoke(HessianSkeleton skeleton, InputStream inputStream, OutputStream outputStream)
throws Throwable {
......
AbstractHessianInput in;
AbstractHessianOutput out;
if (code == 'H') {
// Hessian 2.0 stream
major = isToUse.read();
minor = isToUse.read();
if (major != 0x02) {
throw new IOException("Version " + major + "." + minor + " is not understood");
}
in = new Hessian2Input(isToUse);
out = new Hessian2Output(osToUse);
in.readCall();
}
else if (code == 'C') {
// Hessian 2.0 call... for some reason not handled in HessianServlet!
isToUse.reset();
in = new Hessian2Input(isToUse);
out = new Hessian2Output(osToUse);
in.readCall();
}
else if (code == 'c') {
// Hessian 1.0 call
major = isToUse.read();
minor = isToUse.read();
in = new HessianInput(isToUse);
if (major >= 2) {
out = new Hessian2Output(osToUse);
}
else {
out = new HessianOutput(osToUse);
}
}
......
skeleton.invoke(in, out);
......
}HessianServiceExporter在实例化的同时也初始化了HessianSkeleton对象；又进一步的将Inputstream封装入HessianInput中，将Outputstream封装入Hessian2Output中；接下来把HessianInput和Hessian2Output传入HessianSkeleton中，消息的读取和回复都交给HessianSkeleton来处理；后面的处理具体分析同Hessian入门体验与分析中介绍的。
5.Client接受服务器的回复
具体分析同Hessian入门体验与分析
总结
本文通过hessianJar，hessianClient已经hessianServer三个模块，提供了Spring整合Hessian的实例；通过与Spring的整合，简化了开发；然后从代码层面将包裹在Hessian外层的Spring剥离，还原原始的Hessian调用。
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