使JSF访问Map< String，？>来自EL而不是一个bean字段的值？

问题描述

有没有正确的方法来重写JSF从表达式语言访问bean字段的方式？这个想法是为了访问一个 Map< String，？> 值，模拟这个行为，其中bean字段将是地图键。

$ b换句话说，是否可以使用＃{beanContainingNestedMap.keyOfSaidNestedMap} ，就像 keyOfSaidNestedMap 是 beanContainingNestedMap 的字段？

如果没有，还有什么其他解决方案？

---

示例：

Holder.java

  public class Holder {
 
 private Map< String，Object> objects = new HashMap< String，Object>（）; 
 
 public void add（String key，Object value）{
 objects.put（key，value）; 
} 
 
 public Object getObject（String key）{
 return objects.get（key）; 
} 
 
} 
  

ExampleBean.java

  public class ExampleBean {
 
 private Holder holder =新持有人（）; 
 
 public ExampleBean（）{
 holder.add（foo，42）; 
 holder.add（bar，'X'）; 
} 
 
 public Holder getHolder（）{
 return holder; 
} 
 
} 
  

example.xhtml

 < c：out value =＃{exampleBean.holder.foo} /> <！ - 应该打印42 - > 
< c：out value =＃{exampleBean.holder.bar}/> <！ - 应该打印X - > 
  

---

如果我能做某事喜欢（一种伪代码，因为我不知道这样的方法是否存在;））：

  @Override //覆盖JSF的（如果有的话）
 public Object resolveEl（String el）{
 try {
 super.resolveEl（el）; 
} catch（ElException e）{
 Object bean = e.getBean（）; 
 String fieldName = e.getFieldName（）; 
 if（bean instanceof Holder）{
持有者=（持有者）bean; 
对象值= holder.getObject（fieldName）; 
 if（value == null）{
 throw e; 
} else {
返回值; 
} 
} 
} 
} 
  

解决方案

您可以直接使用地图EL。

Holder.java

  public class Holder {
 
 private Map< String，Object> objects = new HashMap< String，Object>（）; 
 
 public void add（String key，Object value）{
 objects.put（key，value）; 
} 
 
 public Map< String，Object> getObjectsMap（）{
 return objects; 
} 
 
} 
  

EL

 ＃{exampleBean.holder.objectsMap [your-key]} 
  

Is there any proper way to override the way JSF accesses the beans fields from an Expression Language? The idea is to mimic this behavior in order to access a Map<String, ?> values, where the bean fields would be the map keys.

In other words, is it possible anyhow to use #{beanContainingNestedMap.keyOfSaidNestedMap}, just as if keyOfSaidNestedMap were a field of the beanContainingNestedMap?

If not, what other solution may I have?

---

Example:

Holder.java

public class Holder {

    private Map<String, Object> objects = new HashMap<String, Object>();

    public void add(String key, Object value) {
        objects.put(key, value);
    }

    public Object getObject(String key) {
        return objects.get(key);
    }

}

ExampleBean.java

public class ExampleBean {

    private Holder holder = new Holder();

    public ExampleBean() {
        holder.add("foo", 42);
        holder.add("bar", 'X');
    }

    public Holder getHolder() {
        return holder;
    }

}

example.xhtml

<c:out value="#{exampleBean.holder.foo}" /> <!-- should print "42" -->
<c:out value="#{exampleBean.holder.bar}" /> <!-- should print "X" -->

---

What would be great is if I could do something like (kind of pseudo-code since I don't know if such a method exists ;)):

@Override // override JSF's (if any...)
public Object resolveEl(String el) {
    try {
        super.resolveEl(el);
    } catch (ElException e) {
        Object bean = e.getBean();
        String fieldName = e.getFieldName();
        if (bean instanceof Holder) {
            Holder holder = (Holder) bean;
            Object value = holder.getObject(fieldName);
            if (value == null) {
                throw e;
            } else {
                return value;
            }
        }
    }
}

解决方案

You can directly use map by EL.

Holder.java

public class Holder {

    private Map<String, Object> objects = new HashMap<String, Object>();

    public void add(String key, Object value) {
        objects.put(key, value);
    }

    public Map<String, Object> getObjectsMap() {
        return objects;
    }

}

EL

#{exampleBean.holder.objectsMap[your-key]}

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