java枚举自动转换

• 前后端交互枚举转换
• • get请求（参数放url）
  • post请求（参数放body）
• 后端与数据库交互枚举转换

提供两个接口，分别处理以code（int类型）和name（String类型）进行转换的枚举

public interface IFeIntegerEnum {
	
	int getCode();

	static  & IFeIntegerEnum> Optional codeOf(Class enumClass, int value) {
		return Arrays.stream(enumClass.getEnumConstants()).filter(e -> e.getCode() == value).findAny();
	}
}

public interface IFeStringEnum {
	
	int getName();

	static  & IFeStringEnum> Optional codeOf(Class enumClass, String name) {
		return Arrays.stream(enumClass.getEnumConstants()).filter(e -> e.getName().equals(name)).findAny();
	}
}

然后需要两个枚举转换工厂

@Component
public class IntegerToEnumConvertFactory implements ConverterFactory {
	
	@Override
	@Nonnull
	public  Converter getConverter(@Nonnull Class targetType) {
		return new IntegerToEnum(targetType);
	}

	private static class IntegerToEnum & IFeIntegerEnum> implements Converter {
		
		private final Class type;

		public IntegerToEnum(Class type) {
			this.type = type;
		}
	
		@Override
		public T convert(@Nonnull String source) {
			return IFeIntegerEnum.codeOf(this.type,Integer.parseInt(source)).orElseThrow(IllegalArgumentException::new);
		}
	}
}

@Component
public class StringToEnumConvertFactory implements ConverterFactory {
	
	@Override
	@Nonnull
	public  Converter getConverter(@Nonnull Class targetType) {
		return new StringToEnum(targetType);
	}

	private static class StringToEnum & IFeIntegerEnum> implements Converter {
		
		private final Class type;

		public StringToEnum(Class type) {
			this.type = type;
		}
	
		@Override
		public T convert(@Nonnull String source) {
			return IFeStringEnum.codeOf(this.type,source).orElseThrow(IllegalArgumentException::new);
		}
	}
}

最后如何看下实际使用

public enum LolEnum implements IFeIntegerEnum,IFeStringEnum { 

	Q(0,"q技能"),
	W(1,"w技能"),
	E(2,"e技能"),
	R(3,"r技能");
	
	private final int code;
	
	private final String name;

	LolEnum (int code,String name){
		this.code = code;
		this.name = name;
	}
	
	@Override
	public int getCode(){
		return code;
	}

	@Override
	public int getName(){
		return name;
	}
}

则此时无论前端传0,1,2,3还是qwer技能到后端，后端用此枚举都能正常转换，注意这是传参放url的形势，比较麻烦，如果放body就很简单了

此时可以用json工具自动处理，以jackson为例，直接用@JsonCreator和@JsonValue即可

public enum LolEnum { 

	Q(0,"q技能"),
	W(1,"w技能"),
	E(2,"e技能"),
	R(3,"r技能");
	
	private final int code;
	
	private final String name;

	LolEnum (int code,String name){
		this.code = code;
		this.name = name;
	}
	
	
	@JsonCreator
	public static LolEnum valueOfCode(int code ) {
		return Arrays.stream(LolEnum.values()).filter(item -> item.getCode() == code).findFirst().orElseThrow(IllegalArgumentException::new);
	}
	
	
	@JsonValue
	public int getCode(){
		return code;
	}

	public int getName(){
		return name;
	}
}

public interface IDBIntegerEnum {
	
	int getCode();

	static  & IDBIntegerEnum> Optional codeOf(Class enumClass, int value) {
		return Arrays.stream(enumClass.getEnumConstants()).filter(e -> e.getCode() == value).findAny();
	}
}

@MappedTypes(IDBIntegerEnum.class)
@MappedJdbcTypes(JdbcType.INTEGER)
public class IntegerEnumTypeHandler & IDBIntegerEnum> extends baseTypeHandler {

	private final Class type;

	public IntegerEnumTypeHandler(Class type) {
		if(type == null){
			throw new IllegalArgumentException("Type argument cannot be null");
		}
		this.tyoe = type;
	}

	
	 @Override
	 public void setNonNullParameter(PreparedStatement ps,int i,E parameter,JdbcType jdbcType) throws SQLException {
		ps.setInt(i,parameter.getCode());
	}

	
	 @Override
	 public E getNullableResult(ResultSet rs,String columnName) throws SQLException {
		int columnValue = rs.getInt(columnName);
		return rs.wasNull()?null:enumOf(columnValue);
	}

	
	 @Override
	 public E getNullableResult(ResultSet rs,int columnIndex) throws SQLException {
		int columnValue = rs.getInt(columnIndex);
		return rs.wasNull()?null:enumOf(columnValue);
	}

	
	 @Override
	 public E getNullableResult(CallableStatement cs,int columnIndex) throws SQLException {
		int columnValue = cs.getInt(columnIndex);
		return rs.wasNull()?null:enumOf(columnValue);
	}

	private E enumOf(int value){
		return IDBIntegerEnum.codeOf(type,value).orElseThrow(()->new IllegalArgumentException("Cannot convert "+value+" to "+type.getSimpleName()+" by code value."));
	}

}