[Springframework-developer] CGLIB proxies and fields

[Hunter K. <re...@ei...>]

[ This was already sent to the user list, it was suggested I send it on
to the developers list.]

There is some strange behaviour with CGLIB proxied objects and instance 
fields.  Sometime it returns the field of the CGLIB proxy itself, and 
sometimes of the target object, which causes some very unexpected behaviour, 
to say the least.

This is similar to the thread of yesterday, but it petered out somewhat 
inconclusively.  I've boiled it down to a pretty simple sample.

The results are as follows (skipping the initial spring setup stuff):

INFO: Creating implicit proxy for bean 'sampleCommand' with 1 common 
interceptors and 0 specific interceptors
02-Apr-2004 10:45:22 
org.springframework.transaction.support.AbstractPlatformTransactionManager 
commit
INFO: Initiating transaction commit
returned result: <no result>
02-Apr-2004 10:45:22 
org.springframework.transaction.support.AbstractPlatformTransactionManager 
commit
INFO: Initiating transaction commit
method call result: RealCommand result: 3
direct method call result: RealCommand result: 3


Here's the java class and the config file.  The only thing that anyone should
need to change is the properties of the data source...

-- SampleCommand.java

package sample;

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

public class SampleCommand
{
    public static final ApplicationContext appContext = 
initializeAppContext();
    
     private static ApplicationContext initializeAppContext()
     {
         ClassPathXmlApplicationContext ctx = new 
ClassPathXmlApplicationContext("sampleContext.xml");
         return ctx;
     }

    String _result = "<no result>";
    
    public final String execute()
    {
        executeCommand();
        return _result;
    }
    
    public final String executeUsingMethod()
    {
        executeCommand();
        return getResult();
    }

    public String getResult()
    {
        return _result;
    }

    int _foo;
    public void setFoo(int foo)
    { 
        _foo = foo;
    }
    
    public void executeCommand()
    {
        _result = "RealCommand result: "+_foo;
    }
    
    public static  void main(String[] args)
    {
        SampleCommand c = (SampleCommand) appContext.getBean("sampleCommand");
        c.setFoo(3);
        System.out.println("returned result: "+c.execute());
        System.out.println("method call result: "+c.executeUsingMethod());
        System.out.println("direct method call result: "+c.getResult());
    }
}

-- sampleContext.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="sampleCommand" class="sample.SampleCommand"/>

    <!-- Transaction Interceptor set up to do PROPAGATION_REQUIRED on execute 
methods  for Command objects-->
	<bean id="executeMethodTxnAS" 
class="org.springframework.transaction.interceptor.NameMatchTransactionAttributeSource">
	    <property name="properties">
	    	<props>
	    		<prop key="execute*">PROPAGATION_REQUIRED</prop>
	    	</props>
	    </property>
	</bean>
  	
	<bean id="commandExecuteMethodTxnInterceptor" 
class="org.springframework.transaction.interceptor.TransactionInterceptor">
    	<property name="transactionManager"><ref 
local="transactionManager"/></property>
    	<property name="transactionAttributeSource">
    		<!-- I think this uses the spiffy TransactionAttributeSourceEditor, 
obviating the need for a seperate 
    		       TransactionAttributeSource definition in simple cases -->
    		<!-- 
value>com.newbay.mixxe.command.Command.execute=PROPAGATION_REQUIRED</value 
-->
    		<ref local="executeMethodTxnAS"/>
    	</property>
	</bean>

	<!-- One BeanNameAutoProxyCreator handles all beans where we want 
transactions (ie Command.execute) -->
	<bean id="autoProxyCreator" 
class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
	    <property name="interceptorNames">
    		<list><idref local="commandExecuteMethodTxnInterceptor"/></list>
	    </property>
	    <property name="proxyTargetClass"><value>true</value></property>
	    <!-- property name="exposeProxy"><value>true</value></property -->
    	<property name="beanNames">
      		<list><value>*Command</value></list>
	    </property>
  	</bean>
	
	<bean id="transactionManager" 
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource"><ref local="dataSource"/></property>
	</bean>
	
	<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" 
destroy-method="close">
		<property 
name="driverClassName"><value>org.postgresql.Driver</value></property>
		<property 
name="url"><value>jdbc:postgresql://localhost/mixxe</value></property>
		<property name="username"><value>mixxe</value></property>
		<property name="password"><value>mixxe</value></property>
	</bean>
	
	
	
</beans>