constructor exception

[moacir_ha@yahoo.com.br]

Hi,
I have to use a bean (bean2) in the constructor of another bean (bean1), where bean2 is a property of the bean1, but I got a nullpointer exception thrown by the contructor, like the bean2 wasn't initialized. Looks like I can only use bean2 after the constructor. But what do I have to do to use it in the constructor as I got to.

Thanks for the help

[Alarmnummer]

I have left my crystal ball at home today so I think you have to post more information. Please post a small part of you app context where bean1 and 2 are created.

[moacir_ha@yahoo.com.br]

ok
here is the essencial java code:

public class IndexUsuario extends JFrame implements InterfaceIndexUsuario {
private InterfaceControleLogin controleLogin;
private InterfaceControleAvaliacao controleAvaliacao;
private InterfaceAluno aluno;

// metodo set usado pelo Spring
public void setInterfaceControleLogin (InterfaceControleLogin controleLogin) {
this.controleLogin = controleLogin;
}

// metodo set usado pelo Spring
public void setInterfaceControleAvaliacao (InterfaceControleAvaliacao controleAvaliacao) {
this.controleAvaliacao = controleAvaliacao;
}

// metodo set usado pelo Spring
public void setInterfaceAluno (InterfaceAluno aluno) {
this.aluno = aluno;
}

// constructor
public IndexUsuario (InterfaceAluno aluno) {
this.aluno = aluno;

//here controleAvaliacao is null...
controleAvaliacao.anyMetod ();

int larguraJanela = 400; //largura padrao
int alturaJanela = 250; //altura padrao

// seta a localizacao da janela
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
int x1 = (screenSize.width - larguraJanela) / 2;
int y1 = (screenSize.height - alturaJanela) / 2;
setBounds(x1, y1, larguraJanela, alturaJanela);
}

here is the xml config:

<beans>

<bean id="indexUsuario" class="visao.IndexUsuario">
<constructor-arg><ref bean="aluno"/></constructor-arg>
<property name="interfaceControleLogin"><ref bean="controleLogin"/></property>
<property name="interfaceControleAvaliacao"><ref bean="controleAvaliacao"/></property>
<property name="interfaceAluno"><ref bean="aluno"/></property>
</bean>

<bean id="aluno" class="modelo.Aluno">
<property name="interfaceLogin"><ref bean="login"/></property>
</bean>

<bean id="controleAvaliacao" class="controle.ControleAvaliacao">
<property name="interfaceAvaliacao"><ref bean="avaliacao"/></property>
<property name="interfaceConexao"><ref bean="conexao"/></property>
</bean>

<bean id="login" class="modelo.Login"/>
<bean id="conexao" class="controle.Conexao"/>

<bean id="avaliacao" class="modelo.Avaliacao"/>

<bean id="controleLogin" class="controle.ControleLogin">
<property name="interfaceConexao"><ref bean="conexao"/></property>
</bean>

</beans>


Thanks again for the help

[Alarmnummer]

The constructor of IndexUsuario is called before the setters are called, so controleAvaliacao.anyMetod (); will give a nullpointerexception because controleAvaliacio isn`t set.

Why don`t you set all arguments with the constructor? (controleLogin, controleAvaliacao, luno)

Personally I don`t like setter if a constructor is also possible. With a constructor I can guarantee that all my objects are in a consistent state, and I don`t have the obligation of dealing with setters. In some cases a setter is simple, but sometimes I could have enourmous consequences.... that is why I don`t introduce them if it isn`t required.