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JSTL-添加参数以调用[重复]

jstl-functions el jstl java

JavaSheriff · 技术社区 · 7 年前

我在JSTL中有以下代码,用于在j2ee站点中检索学生图片

 <c:if test="${student.studentPictureId != null}">
        <a href="javascript:showImage('<c:out value="${student.studentId}"/>','<c:out value="${student.studentPictureId }"/>
</c:if>

我想让代码更通用
而不是打电话

 student.studentPictureId

学生课堂上的函数签名如下:

  Student class  
           String getPictureId(PictureTypeEnum picture type)

最终的JSTL代码如下:

  <c:if test="${student.getPictureId(PictureTypeEnum.StudentCard) != null}">
        <a href="javascript:showImage('<c:out value="${student.studentId}"/>','<c:out value="${student.getPictureId(PictureTypeEnum.StudentCard)}"/>
</c:if>

我知道打电话的时候

 <c:out value="${student.studentPictureId }"/>

student.studentPictureId

但可以调用学生对象方法并向其传递参数吗?

1 回复 | 直到 7 年前

Maurice Perry 7 年前

无法直接从JSTL调用方法,因此我使用了一种黑客:快速映射:

public abstract class QuickMap<K,V> implements Map<K,V> {
    @Override
    public abstract V get(Object key);

    @Override
    public final int size() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final boolean isEmpty() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final boolean containsKey(Object key) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final boolean containsValue(Object value) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final V put(K key, V value) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final V remove(Object key) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final void putAll(Map<? extends K, ? extends V> m) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final void clear() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final Set<K> keySet() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final Collection<V> values() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public final Set<Entry<K, V>> entrySet() {
        throw new UnsupportedOperationException("Not supported yet.");
    }
}

public Map<Object,String> getStudentPictureIds() {
    return new QuickMap<Object,String>() {
        @Override
        public String get(Object k) {
            PictureTypeEnum type;
            if (k instanceof PictureTypeEnum) {
                type = (PictureTypeEnum)k; 
            } else {
                type = PictureTypeEnum.valueOf(k.toString());
            }
            return getStudentPictureId(type);
        }            
    };
}

并不是说用JSTL操作枚举不容易,所以该方法也接受字符串。

您可以在JSP中使用它,如下所示:

<c:out value="${student.pictureIds['StudentCard']}"/>