ZK Developer's Reference/MVC/Controller/Wire Variables

Wiring Sequence

GenericForwardComposer will wire members defined in the composer. Here is the sequence:

1. It searches any setters if its name matches any of the following
   1. Any fellow with the same name (Component.getFellow(String))
   2. Any variable defined in Page.addVariableResolver(VariableResolver) with the same name
   3. Any variable defined in zscript with the same name
   4. Any implicit object with the same name
2. Then, it searches any field to see if it matches any fellow, any variable,... the same as the above.

Wire Spring-managed Beans

GenericForwardComposer not only wires UI components, but also wires beans that can be found by the registered variable resolvers. Thus, if you'd like GenericForwardComposer to wire the Spring-managed beans, you could register the Spring variable resolver, DelegatingVariableResolver. Then, if a data member's name matches a Spring-managed bean, it will be wired automatically too. For example,

public class PasswordSetter extends GenericForwardComposer {
    private User user; //wired automatically if user is a spring-managed bean
    private Textbox password; //wired automatically if there is a textbox named password

    public void doAfterComposer(Component comp) {
        page.addVariableResolver(new org.zkoss.zkplus.spring.DelegatingVariableResolver());
            //variable resolver must be added before calling super.doAfterCompose
        super.doAfterCompose(comp); //invoke autowiring
    }
    public void onClick$submit() {
        user.setPassword(password.getValue());
    }
}

As shown, we could register the variable resolver in doAfterCompose by use of Page.addVariableResolver(VariableResolver).

Warning: Not a good idea to have Spring managing the composer

There is a tendency to make the composer as a Spring-managed bean. For example, assume we have a composer called passwordSetter and managed by Spring (i.e., annotated with Spring's @Component), then we might do as follows.

<?variable-resolver class="org.zkoss.zkplus.spring.DelegatingVariableResolver"?>
<window apply="${passwordSetter}">
...

@Component
public class PasswordSetter extends GenericForwardComposer {
   @Autowired User user;
...

Unfortunately, this approach is error-prone. The reason is that none of Spring's scopes matches correctly with the lifecycle of the composers. For example, if the Session scope is used, it will cause errors when the user opens two browser windows to visit the same page. In this case, the same composer will be used to serve all desktops in the given session.

If the Prototype scope is used, another new instance will be instantiated if the Spring variable resolver is called to resolve the same name again in the later requests. It sounds unlikely, but it might be triggered implicitly and hard to debug. For example, it happens if some of your code, including data binder, evaluates an EL expression that references the composer's name, when an event received.

If you really want Spring to manage the composers, please use ZK Spring. It extends Spring to provide the scopes matching ZK lifecycle, such as the IdSpace and Component scopes. Please refer to ZK Spring Essentials for more detailed information.

Wire CDI-managed Beans

The approach to work with CDI is similar to the approach for Spring, except the variable resolver for CDI is DelegatingVariableResolver.

zscript and Variable Resolver

By default, variables defined in both zscript and variable resolvers will be checked. There might be some performance penalty if you have too much zscript code, or your variable resolver is too slow.

You could turn them off by passing false to the second and third argument of GenericForwardComposer.GenericForwardComposer(char, boolean, boolean):

public class MyComposer extends GenericForwardComposer {
    public MyComposer() {
        super('$', false, false);
    }
}

Notice if you disable the wiring of EL variables (i.e., variables defined in a variable resolver), you can't wire the Spring-managed beans as described in the previous section.

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ID Space

For components that are inside of another ID space, you could use id1$id2$id3 to access it. More precisely, it will cause GenericForwardComposer to look for id1 in the same ID space as the applied component, and then look for, if found and it is another ID space, id2, and so on. For example, you could find the textbox by inner$input.

<window apply="foo.MyComposer">
   <window id="inner">
        <textbox id="input"/>
...

Here is another example: suppose have two ZUL files:

Main file	Included file - includeme.zul
<window id="mywindow" apply="MyComposer"> <include id="i" src="includeme.zul" /> </window>	<textbox id="username" />

To access the textbox "username" from "MyComposer", you could specify:

public class MyComposer extends GenericAutowireComposer {
    Textbox i$username;
    ...
}

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