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Why method EditOrder in service cannot be invoked? I get error message: java.lang.reflect.InvocationTargetException: null

public class WebServiceSecurity{
	
	private WebServiceSecurityService webServiceSecurityService;
	
	public WebServiceSecurity(){}

	private String EditOrder(String userName, Integer type, Integer startNo, Integer endNo){
		
		return webServiceSecurityService.EditOrder(userName, type, startNo, endNo);
	}

........................
}


public class WebServiceSecurityService {
	private WebServiceSecurityDao webServiceSecurityDao;
	public WebServiceSecurityService(){}
	
	public String EditOrder(String userName, Integer type, Integer startNo, Integer endNo){
..................
}

This is part of applicationContext.xml

	<bean id="webServiceSecurityBean" class="com.ws.WebServiceSecurity" >
	</bean>
	
	<bean id="webServiceSecurityDao" class="com.dao.WebServiceSecurityDao" >
	</bean>
	<bean id="webServiceSecurityService" class="com.service.WebServiceSecurityService">
		<property name="webServiceSecurityDao" ref="webServiceSecurityDao">
		</property>
	</bean>