@ManagedProperty-将一个请求范围内的bean注入另一个请求范围内的bean [英] @ManagedProperty - Inject one request scoped bean into another request scoped bean

问题描述

我有这个 SearchBean :

@ManagedBean(name = "searchBean")
@RequestScoped
public class SearchBean implements Serializable
{
    private String input = null;

    // getter methods
    public String getInput() {
        return input;
    }

    // setter method
    public void setInput(String input) {
        this.input = input;
    }

    public String Submit() {
        return null;
    }    
}

我可以使用@ManagedProperty将其注入另一个bean中.例如:

Can I inject it into another bean using @ManagedProperty. For example:

@ManagedBean(name = "bookBean")
@RequestScoped
public class BookBean implements Serializable
{
    @ManagedProperty(value = "#{searchBean}")
    private SearchBean searchBean;  

    @PostConstruct
    public void init()
    {   
       System.out.println("Value: " + searchBean.getInput());
    }

    public SearchBean getSearchBean() {
       return searchBean;
    }

    public void setSearchBean(SearchBean searchBean) {
       this.searchBean = searchBean;
    }   
}

和Facelet(search.xhtml):

And the Facelet (search.xhtml):

<h:form id="formSearch">
   <h:commandButton value="Search" action="#{searchBean.Submit}" />
</h:form>

更新:我通过ui:insert组件将search.xhtml插入到book.xhtml中，如下所示:

UPDATE: I have search.xhtml inserted into book.xhtml via a ui:insert component as follow:

<h:form id="formBooks">
   <ui:insert name="search">
      <ui:include src="/templates/common/search.xhtml"/>
   </ui:insert> 
</h:form>

上面的searchBean.getInput()方法应作为表单提交的结果返回一个值.以上注射方法可以吗?

The searchBean.getInput() method above should return a value as a result of a form's submission. Is the above method of injection possible?

推荐答案

我假定SearchBean.input将绑定到类似这样的东西:

<h:inputText value="#{searchBean.input}" />

如果是，则为空:

@PostConstruct
public void init()
{   
   System.out.println("Value: " + searchBean.getInput());
}

但是，假设已设置一个值，则在调用此方法时该值不会为空:

But, assuming a value has been set, it will not be null when this method is invoked:

public String Submit() {
    return null;
}

---

---

Richard Hightower的面向非信徒的JSF的图像:JSF应用程序生命周期.

原因归结于JSF生命周期的工作原理:

The reason is due to how the JSF lifecycle works:

1. 第一次解析#{searchBean...}时，发现它不存在:
   • bean被实例化
   • 执行任何依赖项注入(在这种情况下没有任何依赖项)
   • @PostConstruct方法被调用
   • 将bean放入范围内

1. When #{searchBean...} is first resolved and found not to exist:
   • The bean is instantiated
   • Any dependency injections are performed (there aren't any in this case)
   • @PostConstruct method is invoked
   • The bean is placed into scope

此过程在 JSF规范中定义.

现在，如果直接从参数映射中注入SearchBean.input，则在@PostConstruct期间它不会为null:

Now, if SearchBean.input were injected directly from the parameter map, it would not be null during @PostConstruct:

@ManagedProperty(value = "#{param.someParamName}")
private String input;

但是，这没有任何真正的优势-您跳过了任何输入验证，并且不能将SearchBean.input用作字段绑定，因为它将在更新模型值"阶段中被覆盖.

However, there aren't any real advantages to this - you're skipping any input validation and you can't use SearchBean.input as a field binding because it will be overwritten in the Update Model Values phase.

应该使用SearchBean.Submit()方法执行搜索的应用程序逻辑.

The SearchBean.Submit() method is where your application logic for performing the search should go.

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