给枚举添加自定义属性

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mob604756f1e4c7 2018-05-04 14:46:00

文章标签 java经验集锦 JDK 枚举枚举类型字段 文章分类 代码人生

1.常见的枚举是这样的：

public enum AwardsType,

World = 1,

Country = 2,

Provinces=3,

School = 4

};

如果我们要获取额外的信息，比如 world的中文显示，显然上面的写法是不能满足我们的，自己研究了一下，决定给枚举加上自定义属性。加上自定义属性的枚举如下：

[EnumDescription("荣誉奖项")]
        public enum AwardsType

[EnumDescription("世界级")]

World = 1,

[EnumDescription("国家级")]

Country = 2,

[EnumDescription("省市级")]

Provinces=3,

[EnumDescription("校级")]

School = 4

};

注意EnumDescription是自己写的一个类，下面会贴上源码。

2.代码访问：

//0、获得枚举类型的文字描述

string txt = EnumDescription.GetEnumText(typeof(OrderStateEnum));
//1、获得某个枚举值的文字描述： 
string txt = EnumDescription.GetFieldText(OrderStateEnum.Processing)
//2、获得枚举中各个字段的定义数组： 



EnumDescription[] des = EnumDescription.GetFieldTexts(typeof(OrderStateEnum))
//3、如果需要排序，通过他的另一个重载   
public static EnumDescription[] GetFieldTexts( Type enumType, SortType sortType )
//4、绑定到下拉框：



ddlTypeID.DataSource =EnumDescription.GetFieldTexts(typeof(DataHelper.AwardsType));


ddlTypeID.DataTextField = "EnumDisplayText";


ddlTypeID.DataValueField = "EnumValue";


ddlTypeID.DataBind();

3、EnumDescription源码

/// <summary>

/// 把枚举值按照指定的文本显示

/// <remarks>

/// 一般通过枚举值的ToString()可以得到变量的文本，

/// 但是有时候需要的到与之对应的更充分的文本，

/// 这个类帮助达到此目的

/// </remarks>

/// </summary>

/// <example>

/// [EnumDescription("中文数字")]

/// enum MyEnum

/// {

///        [EnumDescription("数字一")]

///     One = 1,

///

///        [EnumDescription("数字二")]

///        Two,

///

///        [EnumDescription("数字三")]

///        Three

/// }

/// EnumDescription.GetEnumText(typeof(MyEnum));

/// EnumDescription.GetFieldText(MyEnum.Two);

/// EnumDescription.GetFieldTexts(typeof(MyEnum));

/// </example>

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Enum)]

public class EnumDescription : Attribute
    {

private string enumDisplayText;

private int enumRank;

private FieldInfo fieldIno;

    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 描述枚举值</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumDisplayText"></span><span style="color: #008000;">描述内容</span><span style="color: #808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumRank"></span><span style="color: #008000;">排列顺序</span><span style="color: #808080;"></param></span></br>
    <span style="color: #0000ff;">public</span> EnumDescription( <span style="color: #0000ff;">string</span> enumDisplayText, <span style="color: #0000ff;">int</span><span style="color: #000000;"> enumRank )</br>
    {</br>
        </span><span style="color: #0000ff;">this</span>.enumDisplayText =<span style="color: #000000;"> enumDisplayText;</br>
        </span><span style="color: #0000ff;">this</span>.enumRank =<span style="color: #000000;"> enumRank;</br>
    }</br></br>

    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 描述枚举值，默认排序为5</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumDisplayText"></span><span style="color: #008000;">描述内容</span><span style="color: #808080;"></param></span></br>
    <span style="color: #0000ff;">public</span> EnumDescription( <span style="color: #0000ff;">string</span><span style="color: #000000;"> enumDisplayText )</br>
        : </span><span style="color: #0000ff;">this</span>(enumDisplayText, <span style="color: #800080;">5</span><span style="color: #000000;">) { }</br></br>

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">string</span><span style="color: #000000;"> EnumDisplayText</br>
    {</br>
        </span><span style="color: #0000ff;">get</span> { <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">this</span><span style="color: #000000;">.enumDisplayText; }</br>
    }</br>

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> EnumRank</br>
    {</br>
        </span><span style="color: #0000ff;">get</span> { <span style="color: #0000ff;">return</span><span style="color: #000000;"> enumRank; }</br>
    }</br>

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> EnumValue</br>
    {</br>
        </span><span style="color: #0000ff;">get</span> { <span style="color: #0000ff;">return</span> (<span style="color: #0000ff;">int</span>)fieldIno.GetValue(<span style="color: #0000ff;">null</span><span style="color: #000000;">); }</br>
    }</br>

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">string</span><span style="color: #000000;"> FieldName</br>
    {</br>
        </span><span style="color: #0000ff;">get</span> { <span style="color: #0000ff;">return</span><span style="color: #000000;"> fieldIno.Name; }</br>
    }</br>

    </span><span style="color: #0000ff;">#region</span>  =========================================对枚举描述属性的解释相关函数</br>

    <span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 排序类型</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">enum</span><span style="color: #000000;"> SortType</br>
    {
        </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
        <span style="color: #808080;">///</span><span style="color: #008000;">按枚举顺序默认排序</br>
        </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>

            Default,

/// <summary>

/// 按描述值排序

/// </summary>

            DisplayText,

/// <summary>

/// 按排序熵

/// </summary>

            Rank


}

    </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> System.Collections.Hashtable cachedEnum = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Hashtable();</br>


    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 得到对枚举的描述文本</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumType"></span><span style="color: #008000;">枚举类型</span><span style="color: #808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><returns></returns></span></br>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">string</span><span style="color: #000000;"> GetEnumText( Type enumType )
    {</br>
        EnumDescription[] eds </span>= (EnumDescription[])enumType.GetCustomAttributes(<span style="color: #0000ff;">typeof</span>(EnumDescription), <span style="color: #0000ff;">false</span><span style="color: #000000;">);</br>
        </span><span style="color: #0000ff;">if</span> ( eds.Length != <span style="color: #800080;">1</span> ) <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">string</span><span style="color: #000000;">.Empty;</br>
        </span><span style="color: #0000ff;">return</span> eds[<span style="color: #800080;">0</span><span style="color: #000000;">].EnumDisplayText;</br>
    }</br>

    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 获得指定枚举类型中，指定值的描述文本。</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumValue"></span><span style="color: #008000;">枚举值，不要作任何类型转换</span><span style="color: #808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><returns></span><span style="color: #008000;">描述字符串</span><span style="color: #808080;"></returns></span></br>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">string</span> GetFieldText( <span style="color: #0000ff;">object</span><span style="color: #000000;"> enumValue )</br>
    {</br>
        EnumDescription[] descriptions </span>=<span style="color: #000000;"> GetFieldTexts(enumValue.GetType(), SortType.Default);</br>
        </span><span style="color: #0000ff;">foreach</span> ( EnumDescription ed <span style="color: #0000ff;">in</span><span style="color: #000000;"> descriptions )</br>
        {</br>
            </span><span style="color: #0000ff;">if</span> ( ed.fieldIno.Name == enumValue.ToString() ) <span style="color: #0000ff;">return</span><span style="color: #000000;"> ed.EnumDisplayText;
        }</br>
        </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">string</span><span style="color: #000000;">.Empty;</br>
    }</br></br>


    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 得到枚举类型定义的所有文本，按定义的顺序返回</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><exception cref="NotSupportedException"></exception></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumType"></span><span style="color: #008000;">枚举类型</span><span style="color: </br>#808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><returns></span><span style="color: #008000;">所有定义的文本</span><span style="color: #808080;"></returns></span></br>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> EnumDescription[] GetFieldTexts( Type enumType )</br>
    {</br>
        </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> GetFieldTexts(enumType, SortType.Default);</br>
    }</br>

    </span><span style="color: #808080;">///</span> <span style="color: #808080;"><summary></span></br>
    <span style="color: #808080;">///</span><span style="color: #008000;"> 得到枚举类型定义的所有文本</br>
    </span><span style="color: #808080;">///</span> <span style="color: #808080;"></summary></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><exception cref="NotSupportedException"></exception></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="enumType"></span><span style="color: #008000;">枚举类型</span><span style="color: #808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><param name="sortType"></span><span style="color: #008000;">指定排序类型</span><span style="color: #808080;"></param></span></br>
    <span style="color: #808080;">///</span> <span style="color: #808080;"><returns></span><span style="color: #008000;">所有定义的文本</span><span style="color: #808080;"></returns></span></br>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> EnumDescription[] GetFieldTexts( Type enumType, SortType sortType )</br>
    {</br>
        EnumDescription[] descriptions </span>= <span style="color: #0000ff;">null</span><span style="color: #000000;">;</br>
        </span><span style="color: #008000;">//</span><span style="color: #008000;">缓存中没有找到，通过反射获得字段的描述信息</span></br>
        <span style="color: #0000ff;">if</span> ( cachedEnum.Contains(enumType.FullName) == <span style="color: #0000ff;">false</span><span style="color: #000000;"> )</br>
        {</br>
            FieldInfo[] fields </span>=<span style="color: #000000;"> enumType.GetFields();</br>
            ArrayList edAL </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ArrayList();</br>
            </span><span style="color: #0000ff;">foreach</span> ( FieldInfo fi <span style="color: #0000ff;">in</span><span style="color: #000000;"> fields )</br>
            {</br>
                </span><span style="color: #0000ff;">object</span>[] eds = fi.GetCustomAttributes(<span style="color: #0000ff;">typeof</span>(EnumDescription), <span style="color: #0000ff;">false</span><span style="color: #000000;">);</br>
                </span><span style="color: #0000ff;">if</span> ( eds.Length != <span style="color: #800080;">1</span> ) <span style="color: #0000ff;">continue</span><span style="color: #000000;">;</br>
                ((EnumDescription)eds[</span><span style="color: #800080;">0</span>]).fieldIno =<span style="color: #000000;"> fi;</br>
                edAL.Add(eds[</span><span style="color: #800080;">0</span><span style="color: #000000;">]);</br>
            }</br>

            cachedEnum.Add(enumType.FullName, (EnumDescription[])edAL.ToArray(</span><span style="color: #0000ff;">typeof</span><span style="color: #000000;">(EnumDescription)));</br>
        }</br>
        descriptions </span>=<span style="color: #000000;"> (EnumDescription[])cachedEnum[enumType.FullName];</br>
        </span><span style="color: #0000ff;">if</span> ( descriptions.Length <= <span style="color: #800080;">0</span> ) <span style="color: #0000ff;">throw</span> <span style="color: #0000ff;">new</span> NotSupportedException(<span style="color: #800000;">"</span><span style="color: #800000;">枚举类型[</span><span style="color: #800000;">"</span> + enumType.Name + <span style="color: #800000;">"</span><span style="color: #800000;">]未定义属性EnumValueDescription</span><span style="color: #800000;">"</span><span style="color: #000000;">);</br>

        </span><span style="color: #008000;">//</span><span style="color: #008000;">按指定的属性冒泡排序</span></br>
        <span style="color: #0000ff;">for</span> ( <span style="color: #0000ff;">int</span> m = <span style="color: #800080;">0</span>; m < descriptions.Length; m++<span style="color: #000000;"> )
        {</br>
            </span><span style="color: #008000;">//</span><span style="color: #008000;">默认就不排序了</span></br>
            <span style="color: #0000ff;">if</span> ( sortType == SortType.Default ) <span style="color: #0000ff;">break</span><span style="color: #000000;">;</br>

            </span><span style="color: #0000ff;">for</span> ( <span style="color: #0000ff;">int</span> n = m; n < descriptions.Length; n++<span style="color: #000000;"> )</br>
            {</br>
                EnumDescription temp;</br>
                </span><span style="color: #0000ff;">bool</span> swap = <span style="color: #0000ff;">false</span><span style="color: #000000;">;</br>

                </span><span style="color: #0000ff;">switch</span><span style="color: #000000;"> ( sortType )</br>
                {
                    </span><span style="color: #0000ff;">case</span><span style="color: #000000;"> SortType.Default:</br>
                        </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</br>
                    </span><span style="color: #0000ff;">case</span><span style="color: #000000;"> SortType.DisplayText:</br>
                        </span><span style="color: #0000ff;">if</span> ( <span style="color: #0000ff;">string</span>.Compare(descriptions[m].EnumDisplayText, descriptions[n].EnumDisplayText) > <span style="color: #800080;">0</span> ) swap = <span style="color: #0000ff;">true</span><span style="color: #000000;">;</br>
                        </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</br>
                    </span><span style="color: #0000ff;">case</span><span style="color: #000000;"> SortType.Rank:</br>
                        </span><span style="color: #0000ff;">if</span> ( descriptions[m].EnumRank > descriptions[n].EnumRank ) swap = <span style="color: #0000ff;">true</span><span style="color: #000000;">;</br>
                        </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</br>
                }</br>

                </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> ( swap )</br>
                {</br>
                    temp </span>=<span style="color: #000000;"> descriptions[m];</br>
                    descriptions[m] </span>=<span style="color: #000000;"> descriptions[n];</br>
                    descriptions[n] </span>=<span style="color: #000000;"> temp;</br>
                }</br>
            }</br>
        }</br>

        </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> descriptions;</br>
    }

    </span><span style="color: #0000ff;">#endregion</span><span style="color: #000000;"></br>
}</span></pre>