在某些场景下我们需要动态生成一些枚举值，主要是通过反射生成，但是这种生成枚举值是不能switch的

1.枚举值类

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 + '\'' +

'}';

}

}

2.生成工具类

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 = enumType.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("============================打印所有枚举(包括固定的和动态的)，可以将数据库中保存的CIC以枚举的形式加载到JVM");

for(CodeInfoEnum codeInfo:CodeInfoEnum.values()){

System.out.println(codeInfo.toString());

}

System.out.println("============================通过codeId找到的枚举，用于PO转VO的处理");

CodeInfoEnum activeStatus_Active = CodeInfoEnum.getByInfoId(3L);

System.out.println(activeStatus_Active);

System.out.println("============================通过ClassId找到的枚举列表");

List activeStatusEnumList = CodeInfoEnum.getByClassId(3L);

for(CodeInfoEnum codeInfo : activeStatusEnumList){

System.out.println(codeInfo);

}

System.out.println("============================通过ClassCode和InfoCode获取枚举，用于导入验证CIC合法性");

CodeInfoEnum toGetActiveStatus_Active = CodeInfoEnum.getByClassCodeAndInfoCode("ActiveStatus","Active");

System.out.println(toGetActiveStatus_Active);

System.out.println("============================通过ClassCode和InfoCode获取枚举，输入不存在的Code，则返回NULL");

CodeInfoEnum toGetActiveStatus_miss = CodeInfoEnum.getByClassCodeAndInfoCode("ActiveStatus","MISS");

System.out.println(toGetActiveStatus_miss);

}

}