摘要：一個(gè)思路，是將枚舉項(xiàng)保存在數(shù)據(jù)庫里，項(xiàng)目啟動或定時(shí)刷新枚舉項(xiàng)。在項(xiàng)目中，只定義枚舉類型，比如在接口中，使用就可以獲取枚舉，并傳入后面的處理層了。

在項(xiàng)目中，會存在很多枚舉，比如下面顏色和水果的枚舉，COLOR[RED(1),GREEN(2),BLUE(3)],FRUIT[APPLE(4),BANANA(5),ORANGE(6)]，但是問題是，如果要增加枚舉類型，就會涉及修改代碼的問題，一個(gè)比較常見的例子是，枚舉生成一個(gè)列表，供前臺選擇，如果增加類型，那么前后臺都需要進(jìn)行修改。
一個(gè)思路，是將枚舉項(xiàng)保存在數(shù)據(jù)庫里，項(xiàng)目啟動或定時(shí)刷新枚舉項(xiàng)。在項(xiàng)目中，只定義枚舉類型，比如

public enum COLOR{}
public enum FRUIT{}

在接口中，使用COLOR.valueOf()就可以獲取枚舉，并傳入后面的處理層了。為什么要使用枚舉呢？類型安全么，只要可以獲取枚舉，就說明前臺傳的值是正確的，即進(jìn)行了范圍校驗(yàn)。

代碼是參考了一篇文章https://www.niceideas.ch/roll...
有興趣的可以看一下。他的例子，是在一個(gè)數(shù)據(jù)庫表里面有一張類似業(yè)務(wù)流水表，上面有一個(gè)CODE字段，代碼了對記錄的不同處理，CODE很多，他不想手寫大量的if...else語句，想轉(zhuǎn)成enum進(jìn)行處理（這個(gè)我還沒有相同，動態(tài)的enum也沒辦法直接在代碼上switch case，那么是不是他在生成的枚舉上，包含了調(diào)用的方法）。
下面是在他代碼之上，進(jìn)行了些許的修改,便于適應(yīng)我自己的業(yè)務(wù)場景。

public enum CodeInfoEnum {
    LOCK(1L,1L,"LOCK_TYPE","LOCK"),UNLOCK(1L,2L,"LOCK_TYPE","LOCK");
    public Long classId;
    public Long infoId;
    public String classCode;
    public String infoCode;
    CodeInfoEnum(Long classId,Long infoId,String classCode,String infoCode){
        this.classId = classId;
        this.infoId = infoId;
        this.classCode = classCode;
        this.infoCode = infoCode;
    }
    public static CodeInfoEnum getByInfoId(Long infoId){
        return CodeInfoEnum.valueOf(infoId+"");
    }
    public static List getByClassId(Long classId){
        return Arrays.stream(CodeInfoEnum.values()).filter(item->item.classId.equals(classId)).collect(Collectors.toList());
    }
    public static CodeInfoEnum getByClassCodeAndInfoCode(String classCode,String infoCode){
        Optional opt = Arrays.stream(CodeInfoEnum.values()).filter(item->item.classCode.equals(classCode)&&item.infoCode.equals(infoCode)).findFirst();
        return opt.orElse(null);
    }

    @Override
    public String toString() {
        return "CodeInfoEnum{" +
                "classId=" + classId +
                ", infoId=" + infoId +
                ", classCode="" + classCode + """ +
                ", infoCode="" + infoCode + """ +
                "}";
    }
}

public class DynamicEnumTest {
    private static ReflectionFactory reflectionFactory = ReflectionFactory.getReflectionFactory();
    private static void setFailsafeFieldValue(Field field, Object target, Object value) throws NoSuchFieldException,
            IllegalAccessException {

        // let"s make the field accessible
        field.setAccessible(true);
        // next we change the modifier in the Field instance to
        // not be final anymore, thus tricking reflection into
        // letting us modify the static final field
        Field modifiersField = Field.class.getDeclaredField("modifiers");
        modifiersField.setAccessible(true);
        int modifiers = modifiersField.getInt(field);

        // blank out the final bit in the modifiers int
        modifiers &= ~Modifier.FINAL;
        modifiersField.setInt(field, modifiers);

        FieldAccessor fa = reflectionFactory.newFieldAccessor(field, false);
        fa.set(target, value);
    }
    private static void blankField(Class enumClass, String fieldName) throws NoSuchFieldException,
            IllegalAccessException {
        for (Field field : Class.class.getDeclaredFields()) {
            if (field.getName().contains(fieldName)) {
                AccessibleObject.setAccessible(new Field[] { field }, true);
                setFailsafeFieldValue(field, enumClass, null);
                break;
            }
        }
    }

    private static void cleanEnumCache(Class enumClass) throws NoSuchFieldException, IllegalAccessException {
        blankField(enumClass, "enumConstantDirectory"); // Sun (Oracle?!?) JDK 1.5/6
        blankField(enumClass, "enumConstants"); // IBM JDK
    }
    private static ConstructorAccessor getConstructorAccessor(Class enumClass, Class[] additionalParameterTypes)
            throws NoSuchMethodException {
        Class[] parameterTypes = new Class[additionalParameterTypes.length + 2];
        parameterTypes[0] = String.class;
        parameterTypes[1] = int.class;
        System.arraycopy(additionalParameterTypes, 0, parameterTypes, 2, additionalParameterTypes.length);
        return reflectionFactory.newConstructorAccessor(enumClass.getDeclaredConstructor(parameterTypes));
    }

    private static Object makeEnum(Class enumClass, String value, int ordinal, Class[] additionalTypes,
                                   Object[] additionalValues) throws Exception {
        Object[] parms = new Object[additionalValues.length + 2];
        parms[0] = value;
        parms[1] = Integer.valueOf(ordinal);
        System.arraycopy(additionalValues, 0, parms, 2, additionalValues.length);
        return enumClass.cast(getConstructorAccessor(enumClass, additionalTypes).newInstance(parms));
    }

    /**
     * Add an enum instance to the enum class given as argument
     *
     * @param  the type of the enum (implicit)
     * @param enumType the class of the enum to be modified
     * @param enumName the name of the new enum instance to be added to the class.
     */
    @SuppressWarnings("unchecked")
    public static > void addEnum(Class enumType, String enumName,Class[] paramClass,Object[] paramValue) {

        // 0. Sanity checks
        if (!Enum.class.isAssignableFrom(enumType)) {
            throw new RuntimeException("class " + enumType + " is not an instance of Enum");
        }

        // 1. Lookup "$VALUES" holder in enum class and get previous enum instances
        Field valuesField = null;
        Field[] fields = CodeInfoEnum.class.getDeclaredFields();
        for (Field field : fields) {
            if (field.getName().contains("$VALUES")) {
                valuesField = field;
                break;
            }
        }
        AccessibleObject.setAccessible(new Field[] { valuesField }, true);

        try {

            // 2. Copy it
            T[] previousValues = (T[]) valuesField.get(enumType);
            List values = new ArrayList(Arrays.asList(previousValues));

            // 3. build new enum
            T newValue = (T) makeEnum(enumType, // The target enum class
                    enumName, // THE NEW ENUM INSTANCE TO BE DYNAMICALLY ADDED
                    values.size(),
                    //new Class[] {}, // could be used to pass values to the enum constuctor if needed
                    paramClass,
                    //new Object[] {}
                    paramValue
            ); // could be used to pass values to the enum constuctor if needed

            // 4. add new value
            values.add(newValue);
            Object object=values.toArray((T[]) Array.newInstance(enumType, 0));
            // 5. Set new values field
            setFailsafeFieldValue(valuesField, null, object);

            // 6. Clean enum cache
            cleanEnumCache(enumType);

        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    public static void main(String[] args) {

        //
        synchronized (CodeInfoEnum.class) {
            addEnum(CodeInfoEnum.class, "3", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{2L, 3L, "ActiveStatus", "Active"});
            addEnum(CodeInfoEnum.class, "4", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{2L, 4L, "ActiveStatus", "Inactive"});
            addEnum(CodeInfoEnum.class, "5", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{3L, 5L, "Optype", "OP1"});
            addEnum(CodeInfoEnum.class, "6", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{3L, 6L, "Optype", "OP2"});
            addEnum(CodeInfoEnum.class, "7", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{3L, 7L, "Optype", "OP3"});
            addEnum(CodeInfoEnum.class, "8", new Class[]{Long.class, Long.class, String.class, String.class}, new Object[]{3L, 8L, "Optype", "OP4"});
        }
        CodeInfoEnum codeInfoEnum =CodeInfoEnum.valueOf("5");
        System.out.println(codeInfoEnum);
        // Run a few tests just to show it works OK.
        System.out.println(Arrays.deepToString(CodeInfoEnum.values()));
        System.out.println("============================打印所有枚舉（包括固定的和動態(tài)的），可以將數(shù)據(jù)庫中保存的CIC以枚舉的形式加載到JVM");
        for(CodeInfoEnum codeInfo:CodeInfoEnum.values()){
            System.out.println(codeInfo.toString());
        }

        System.out.println("============================通過codeId找到的枚舉，用于PO轉(zhuǎn)VO的處理");
        CodeInfoEnum activeStatus_Active = CodeInfoEnum.getByInfoId(3L);
        System.out.println(activeStatus_Active);

        System.out.println("============================通過ClassId找到的枚舉列表");
        List activeStatusEnumList = CodeInfoEnum.getByClassId(3L);
        for(CodeInfoEnum codeInfo : activeStatusEnumList){
            System.out.println(codeInfo);
        }

        System.out.println("============================通過ClassCode和InfoCode獲取枚舉，用于導(dǎo)入驗(yàn)證CIC合法性");
        CodeInfoEnum toGetActiveStatus_Active = CodeInfoEnum.getByClassCodeAndInfoCode("ActiveStatus","Active");
        System.out.println(toGetActiveStatus_Active);

        System.out.println("============================通過ClassCode和InfoCode獲取枚舉，輸入不存在的Code，則返回NULL");
        CodeInfoEnum toGetActiveStatus_miss = CodeInfoEnum.getByClassCodeAndInfoCode("ActiveStatus","MISS");
        System.out.println(toGetActiveStatus_miss);


    }
}

我將項(xiàng)目中所有的枚舉，都定義在了CodeInfoEnum中，其中包含兩部分，一部分是固定的枚舉，我是預(yù)定義的，比如記錄狀態(tài)（有效|刪除），鎖定狀態(tài)（可用|鎖定）等，這些的枚舉字面值是英文大寫單詞；另一部分是動態(tài)的，具有比較強(qiáng)的業(yè)務(wù)含義，比如倉庫管理中的庫位類型，包裝類型這些，這些的枚舉字面值是數(shù)字，即數(shù)據(jù)庫中的ID。

在使用的使用，注意：

在和前臺交互的時(shí)候，統(tǒng)一使用字面值

在校驗(yàn)的時(shí)候，使用class_code和字面值進(jìn)行校驗(yàn)。

在controller進(jìn)行參數(shù)組裝的時(shí)候，將前臺傳入的字面值轉(zhuǎn)成CodeInfoEnum

在持久化的時(shí)候使用字面值

查詢的時(shí)候，將數(shù)據(jù)庫中的字面值轉(zhuǎn)化為CodeInfoEnum

上面寫的‘使用’，目前還是設(shè)想，還沒有動手實(shí)現(xiàn)。也是我下面準(zhǔn)備做的。希望有看到本文的大神，如能提供寶貴意見，將不勝感激。