从 JSF 传递 Enum 值作为参数（重访）

发布于 2024-11-17 10:36:45 字数 1094 浏览 7 评论 0原文

从 JSF 传递 Enum 值作为参数

问题已经涉及这个问题，但是提议的解决方案对我不起作用。我在支持 bean 中定义了以下枚举：

public enum QueryScope {
  SUBMITTED("Submitted by me"), ASSIGNED("Assigned to me"), ALL("All items");

  private final String description;

  public String getDescription() {
    return description;
  }

  QueryScope(String description) {
    this.description = description;
  }
}

然后我将其用作方法参数

public void test(QueryScope scope) {
  // do something
}

并通过 EL 在我的 JSF 页面中使用它

<h:commandButton
      id        = "commandButton_test"
      value     = "Testing enumerations"
      action    = "#{backingBean.test('SUBMITTED')}" />

到目前为止一切顺利 - 与原始问题中提出的问题相同。但是，我必须处理 javax.servlet.ServletException: Method not find: %complete_qualified_package_name%.BackingBean.test(java.lang.String)。

所以看来 JSF 正在解释方法调用，就好像我想调用一个以 String 作为参数类型的方法（当然不存在） - 因此不会发生隐式转换。

是什么因素导致该示例中的行为与上述示例不同？

原文

Passing a Enum value as a parameter from JSF

This question already deals with this issue, however the proposed solution has not worked for me. I define the following enumeration in my backing bean:

public enum QueryScope {
  SUBMITTED("Submitted by me"), ASSIGNED("Assigned to me"), ALL("All items");

  private final String description;

  public String getDescription() {
    return description;
  }

  QueryScope(String description) {
    this.description = description;
  }
}

Then I use it as a method parameter

public void test(QueryScope scope) {
  // do something
}

And use it via EL in my JSF page

<h:commandButton
      id        = "commandButton_test"
      value     = "Testing enumerations"
      action    = "#{backingBean.test('SUBMITTED')}" />

So far so good - identical to the problem posed in the original question. However I have to deal with a javax.servlet.ServletException: Method not found: %fully_qualified_package_name%.BackingBean.test(java.lang.String).

So it seems that JSF is interpreting the method call as if I would like to call a method with String as parameter type (which of course does not exist) - therefore no implicit conversion takes place.

What could be the factor that makes the behavior differ in this example from the aforelinked?

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安穩 2024-11-24 10:36:45

在您的 backingBean 中，您可能已经编写了带有 enum 参数的方法：

<!-- This won't work, EL doesn't support Enum: -->
<h:commandButton ... action="#{backingBean.test(QueryScope.SUBMITTED)}" />

// backingBean:
public void test(QueryScope queryScope) {
    // your impl
}

但是，建议的解决方案 不使用枚举，而是使用 字符串。那是因为 EL 根本不支持枚举：

<!-- This will work, EL does support String: -->
<h:commandButton ... action="#{backingBean.test('SUBMITTED')}" />    

// backingBean:
public void test(String queryScopeString) {
    QueryScope queryScope = QueryScope.valueOf(queryScopeString);
    // your impl
}

In your backingBean, you may have written a method with the enum parameter:

<!-- This won't work, EL doesn't support Enum: -->
<h:commandButton ... action="#{backingBean.test(QueryScope.SUBMITTED)}" />

// backingBean:
public void test(QueryScope queryScope) {
    // your impl
}

But, the proposed solution does not use enum, it uses String. That's because EL doesn't support enum at all:

<!-- This will work, EL does support String: -->
<h:commandButton ... action="#{backingBean.test('SUBMITTED')}" />    

// backingBean:
public void test(String queryScopeString) {
    QueryScope queryScope = QueryScope.valueOf(queryScopeString);
    // your impl
}

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