如何获取selectManyCheckBox返回除List< String>以外的内容? [英] How do I get selectManyCheckBox to return something other than List<String>?

问题描述

这是一种模式，如果我可以使用的话，我会一遍又一遍地使用它.我有一个枚举名称Log.LogKey，我想让用户从中选取实例.因此，facelet具有以下功能:

This is a pattern that I would use over and over again if I get it to work. I have an enum name Log.LogKey that I want to user to pick out instances of. So the facelet has this:

             <h:form id="testForm" >

                <h:selectManyCheckbox value="#{test.selectedKeys}" >
                    <f:selectItems value="#{test.allKeys}"
                                   var="lk"
                                   itemLabel="#{lk.display}"
                                   itemValue="#{lk}" />
                </h:selectManyCheckbox>

                <h:commandButton value="Do It" action="#{test.doNothng}" />

            </h:form>

该枚举有一个名为 getDisplay()的吸气剂. selectItems 属性可正确调用该字符串，因为这是呈现给用户的字符串.支持豆具有以下功能:

The enum has a getter called getDisplay(). The selectItems attribute calls that correctly because that's the string that gets rendered to the user. And the backing bean has this:

public class Test implements Serializable {

private List<Log.LogKey> selectedKeys = null;

public List<Log.LogKey> getAllKeys() {
    return Arrays.asList(Log.LogKey.values());
}

public List<Log.LogKey> getSelectedKeys() { return selectedKeys; }

public void setSelectedKeys(List selected) {
    System.out.println("getSelecgedKeus() got " + selected.size());
    int i = 0;
    for (Object obj : selected) {
        System.out.println(i++ + " is " + obj.getClass() + ":" + obj);
    }
}

public String doNothng() { return null; }

}

因此，在提交表单时，将使用字符串列表而不是Log.LogKey列表来调用数组 setSelectedKeys(选定).在 selectItems 标记中对#{lk} 的引用将对象转换为字符串.正确的方法是什么?

So on the form submit, the array setSelectedKeys(selected) gets called with a List of Strings, not a List of Log.LogKey. The reference to #{lk} in the selectItems tag is converting the object to a string. What would be the right way to do this?

推荐答案

您需要指定一个转换器. JSF EL不了解泛型List类型，因为在运行时该类型会丢失.当您未明确指定转换器时，JSF不会转换提交的String值，并用它们简单地填充列表.

You need to specify a converter. JSF EL is not aware about the generic List type because that's lost during runtime. When you do not explicitly specify a converter, JSF will not convert the submitted String values and plain fill the list with them.

在特定情况下，您可以使用内置的JSF

In your particular case, you can make use of the JSF builtin EnumConverter, you just have to super() the enum type in the constructor:

package com.example;

import javax.faces.convert.EnumConverter;
import javax.faces.convert.FacesConverter;

@FacesConverter(value="logKeyConverter")
public class LogKeyConverter extends EnumConverter {

    public LogKeyConverter() {
        super(Log.LogKey.class);
    }

}

要使用它，只需声明如下:

To use it, just declare it as follows:

<h:selectManyCheckbox value="#{test.selectedKeys}" converter="logKeyConverter">
    ...
</h:selectManyCheckbox>

另请参见:

• 在h:selectManyCheckbox中使用枚举

See also:

• Use enum in h:selectManyCheckbox

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