problem when transfering a pojo object by using hessian

[henryzhou]

Hi All,

Here's the xml configuration and class definition of my environment.

<bean id="simpleObject" class="example.SimpleObject">
    	<property name="accountService" ref="hessianService"/>
    </bean>
    
<bean id="hessianService" class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
    	<property name="serviceUrl" value="http://localhost:7080/spring/hessian/AccountService"/>
    	<property name="serviceInterface" value="example.AccountService"/>
</bean>

package example;

import java.util.*;

public interface AccountService{
	public Order getOrder(String id);
	public Date getCurrentDate();
}

package example;

import java.util.*;

public interface Order{
	public Date getOrderDate();
	public String getOrderId();
}

package example;

import java.util.*;

public class AccountServiceImpl implements AccountService{
        public Order getOrder(String id){
                Order order = new OrderImpl(id);
                return order;
        }
        public Date getCurrentDate(){
                return new Date();
        }
}

package example;

import java.io.*;
import java.util.*;

public class OrderImpl implements Order, Serializable{
        private String id;
        private Date date;

        public OrderImpl(String id){
                this.id = id;
                this.date = new Date();
        }

        public Date getOrderDate(){
                return this.date;
        }

        public String getOrderId(){
                return this.id;
        }
}

Here, in my class SimpleObject, I could call the method getCurrentDate() of instance accountService and get the correct result. But if I call getOrder("100"), it will remind me the following exception.

java.lang.InstantiationException: example.Order
at java.lang.Class.newInstance0(Class.java:293)
at java.lang.Class.newInstance(Class.java:261)
at com.caucho.hessian.io.JavaDeserializer.instantiate (JavaDeserializer.java:172)
at com.caucho.hessian.io.JavaDeserializer.readMap(Jav aDeserializer.java:112)
at com.caucho.hessian.io.HessianInput.readObject(Hess ianInput.java:662)
at com.caucho.hessian.io.HessianInput.readReply(Hessi anInput.java:241)
at com.caucho.hessian.client.HessianProxy.invoke(Hess ianProxy.java:179)
at $Proxy0.getOrder(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.remoting.caucho.HessianClientI nterceptor.invoke(HessianClientInterceptor.java:11 5)
at org.springframework.aop.framework.ReflectiveMethod Invocation.proceed(ReflectiveMethodInvocation.java :170)
at org.springframework.aop.framework.JdkDynamicAopPro xy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy1.getOrder(Unknown Source)
at example.SimpleObject.printOrder(SimpleObject.java: 15)
at example.SimpleObject.main(SimpleObject.java:23)
Exception in thread "main" org.springframework.remoting.RemoteAccessException : Cannot access Hessian service at [http://localhost:7080/spring/hessian/AccountService]; nested exception is java.io.IOException: java.lang.InstantiationException: example.Order
java.io.IOException: java.lang.InstantiationException: example.Order
at com.caucho.hessian.io.JavaDeserializer.readMap(Jav aDeserializer.java:119)
at com.caucho.hessian.io.HessianInput.readObject(Hess ianInput.java:662)
at com.caucho.hessian.io.HessianInput.readReply(Hessi anInput.java:241)
at com.caucho.hessian.client.HessianProxy.invoke(Hess ianProxy.java:179)
at $Proxy0.getOrder(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.remoting.caucho.HessianClientI nterceptor.invoke(HessianClientInterceptor.java:11 5)
at org.springframework.aop.framework.ReflectiveMethod Invocation.proceed(ReflectiveMethodInvocation.java :170)
at org.springframework.aop.framework.JdkDynamicAopPro xy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy1.getOrder(Unknown Source)
at example.SimpleObject.printOrder(SimpleObject.java: 15)
at example.SimpleObject.main(SimpleObject.java:23)

Any hints?

Thank you

[jwray]

Hi,

I've never used the Hessian protocol but it looks from your stack trace that it's trying to construct an instance of the Order interface rather than the implementation class.

I'd either look into the Hessian docs and see if it has anything to say about that, and/or change the service methods to remove the Order interface and just return the implementation.

Jonny

[henryzhou]

Hi,

I've never used the Hessian protocol but it looks from your stack trace that it's trying to construct an instance of the Order interface rather than the implementation class.

I'd either look into the Hessian docs and see if it has anything to say about that, and/or change the service methods to remove the Order interface and just return the implementation.

Jonny

Hi jwray,

Thank you. You're right. If I change the return type of method getOrder from interface Order to its implementation class OrderImpl could solve the problem.

So that means I can hide the detail implementation class from its interface, right? Maybe I should design some adapters to transfer the objects.

Thank you for your answer.

Any hints about that?