Autowiring in Prototype Bean

Question

I am creating a financial application using Swing with Spring. In one portion of my application I have a JList containing a JLabel for each Account in the application. When the JLabel is clicked, I want to display a JPanel of type AccountTab within a JTabbedPane. This is all performed in the following controller.

@Component
public class AccountListController extends MouseAdapter implements MouseListener {

    @Autowired
    private AccountService accountService;

    @Autowired
    private MainFrameView mainFrameView;

    @Autowired
    private ApplicationContext context;

    @Override
    public void mouseClicked(MouseEvent e) {
        if (e.getSource() instanceof JList) {
            JList list = (JList) e.getSource();
            JTabbedPane tabbedPane = this.mainFrameView.getTabbedPane();

            SidebarItem item = (SidebarItem) list.getModel().getElementAt(list.getSelectedIndex());
            Account account = accountService.findById(item.getValue());

            if (tabbedPane.indexOfTab(account.getName()) == -1) {
                AccountTab panel = context.getBean(AccountTab.class);
                panel.addTransactions(account.getTransactions());
                panel.getSplitPane().setDividerLocation(500);
                tabbedPane.addTab(item.getTitle(), panel);
            }

            tabbedPane.setSelectedIndex(tabbedPane.indexOfTab(account.getName()));
        }
    }

}

The AccountTab changes for each JLabel clicked so I made AccountTab a prototype bean, so I receive a new instance for each account. In order to make the prototype scope work, I need to use context.getBean(AccountTab.class). Here is the AccountTab code:

@Component
@Scope("prototype")
public class AccountTab extends JPanel {

    @Autowired
    private AccountTransactionPane transactionPane;

    private static final long serialVersionUID = 1L;
    private JTable table = new JTable();
    private JSplitPane splitPane;

    public AccountTab() {
        this.setLayout(new BorderLayout());
        JScrollPane scrollPane = new JScrollPane(this.table);
        splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, scrollPane, transactionPane);
        splitPane.setEnabled(false);
        this.add(splitPane, BorderLayout.CENTER);
    }

    public void addTransactions(List transactions) {
        this.table.setModel(new AccountTransactionTableModel(transactions));
    }

    //omitted rest of code
}

You will notice I attempt to autowire a bean of type AccountTransactionPane however, the bean is not properly autowired, it is null. Here is the code for AccountTransactionPane:

@Component
public class AccountTransactionPane extends JPanel {

    private static final long serialVersionUID = 1L;

    JTabbedPane tabbedPane = new JTabbedPane();
    private JPanel withdrawlTransactionPane = new DepositTransactionPane().build();
    private JPanel depositTransactionPane = new DepositTransactionPane().build();
    private JPanel transferTransactionPane = new DepositTransactionPane().build();

    public AccountTransactionPane() {
        this.setLayout(new BorderLayout());
        tabbedPane.addTab("Withdrawl", this.withdrawlTransactionPane);
        tabbedPane.addTab("Deposit", this.depositTransactionPane);
        tabbedPane.addTab("Transfer", this.transferTransactionPane);
        this.add(tabbedPane, BorderLayout.CENTER);
    }
    //rest of class omitted
}

I have one specific problem and one general. First, the AccountTransactionPane is not autowired within the AccountTab bean. I am not sure why, how can I get the AccountTransactionPane bean to be autowired within AccountTab?

My second problem is more general, I am autowiring everything. It seems like everything needs to be a bean. I have fallen into the pattern of create a controller(bean), inject the UI(bean), then inject another controller(bean) which is used as the listener, within that controller I inject a service(bean). Is this normal? I can't find any good examples of large Swing with Spring applications to guide me.

UPDATE: Spring Java Config

@Configuration
@EnableJpaRepositories(basePackages="rhcloud.blog.tothought.data.repositories")
@EnableTransactionManagement
@ComponentScan({"rhcloud.blog.tothought.data", "rhcloud.blog.tothought.controllers", "rhcloud.blog.tothought.view.ui"})
public class ApplicationConfiguration {

      private static final String H2_JDBC_URL_TEMPLATE = "jdbc:h2:file:~/MyFinances/data;TRACE_LEVEL_FILE=3;TRACE_LEVEL_SYSTEM_OUT=3";

      @Bean
      public DataSource dataSource(){
            JdbcDataSource ds = new JdbcDataSource();       
            ds.setURL(H2_JDBC_URL_TEMPLATE);
            ds.setUser("sa");
            ds.setPassword("sa");

            return ds;
      }

      @Bean
      public EntityManagerFactory entityManagerFactory() {

        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setGenerateDdl(true);
        vendorAdapter.setShowSql(true);
        vendorAdapter.setDatabase(Database.H2);

        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("rhcloud.blog.tothought.data.entities");
        factory.setDataSource(dataSource());
        factory.afterPropertiesSet();

        return factory.getObject();
      }

      @Bean
      public PlatformTransactionManager transactionManager() {
        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory());
        return txManager;
      }

      /**
       * See: http://stackoverflow.com/questions/8434712/no-persistence-exception-translators-found-in-bean-factory-cannot-perform-excep
       * @return
       */
      @Bean 
        public HibernateExceptionTranslator hibernateExceptionTranslator(){ 
          return new HibernateExceptionTranslator(); 
        }

      @Bean
      public Application application(){
          return new Application();
      }
}

Sotirios Delimanolis · Accepted Answer

The injection process goes like this

Get Class instance for the class to create a bean for
Either get a Constructor or use Class#newInstance() to create the bean
Inject the bean with all of its @Autowired targets.

Your class' constructor is like

@Autowired
private AccountTransactionPane transactionPane;

...

public AccountTab() {
    this.setLayout(new BorderLayout());
    JScrollPane scrollPane = new JScrollPane(this.table);
    splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, scrollPane, transactionPane);
    splitPane.setEnabled(false);
    this.add(splitPane, BorderLayout.CENTER);
}

So obviously transactionPane is going to be null in the constructor. Spring hasn't gotten around to injecting it. Consider using a @PostConstruct annotated method if there is some initialization you need to do with the injected beans.

My second problem is more general, I am autowiring everything. It seems like everything needs to be a bean. I have fallen into the pattern of create a controller(bean), inject the UI(bean), then inject another controller(bean) which is used as the listener, within that controller I inject a service(bean). Is this normal?

There should be one entry point to your application that loads the Spring ApplicationContext. Every other component (and its dependencies) should be managed by that ApplicationContext.

Autowiring in Prototype Bean

Answers (2)

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