Java 传递参数后获取空值

我正在试图弄清楚为什么

FinalTransactionSortableField.fromCode（orderBy）

的值为null。我正在使用一个REST客户端 参数被传递到以下控制器方法中

我的控制器类中有以下方法：

public ResponseEntity<SetRESTData<FinancialTransactionDTO>> getTFIUse(

    @RequestParam(value = "bId", required = true) final String bId,
    @RequestParam(value = "status", required = false) final String statusString,
    @RequestParam(value = "transactionMethod", required = false) final String transactionMethodString,
    @RequestParam(value = "sortBy", required = false) final String orderBy,
    @RequestParam(value = "sortDirection", required = false) final String sortDirectionString) {

    //line 76 below 
    final FinancialTransactionPaginationData paginationData = StringUtils.isBlank(orderBy) ?
      null : new FinancialTransactionPaginationData(FinancialTransactionSortableField.fromCode(orderBy), null, null, sortDirectionString);
    //line# 79 below  
    final ServiceResultDetails<Set<FinancialTransactionDTO>> resultsDetails =
      financialTransactionService.getTransactionsForEmployeeUse(businessId,status, method, paginationData);

  }

当我将调试点放在第61行（return语句）时，我可以在eclipse中的调试器上看到值

createdTs

，如下所示：

public enum FinancialTransactionSortableField implements MappableEnum<FinancialTransactionSortableField>, SortableField {

  ID(DefaultSortableField.ID.getCode(), "Transaction Id", DefaultSortableField.ID.getColumnName()),
  CASH_AMOUNT("CashAmount", "Cash Amount", "cashAmount"),
  SECURITY_AMOUNT("SecurityAmount", "Security Amount", "securityAmount"),
  STATUS("Status", "Status", "status"),
  CREATED_TS(DefaultSortableField.CREATED_TS.getCode(),
             DefaultSortableField.CREATED_TS.getDescription(),
             DefaultSortableField.CREATED_TS.getColumnName()),;

  private final String code;
  private final String description;
  private final String columnName;

  private static final Map<String, FinancialTransactionSortableField> CODE_MAP =
    MappableEnumUtil.buildCodeMap(FinancialTransactionSortableField.class);

  private FinancialTransactionSortableField(final String code, final String description, final String columnName) {
    this.code = code;
    this.description = description;
    this.columnName = columnName;
  }

  @JsonValue
  @Override
  public String getCode() {
    return code;
  }

  @Override
  public String getDescription() {
    return description;
  }

  @Override
  public String getColumnName() {
    return columnName;
  }

  @Override
  public FinancialTransactionSortableField toEnum(final String code) {
    return fromCode(code);
  }

  @JsonCreator
  public static FinancialTransactionSortableField fromCode(final String code) {
    return CODE_MAP.get(code);
  }

}

供参考：

1）

code\u映射

是在类FinancialTransactionSortable字段中定义的映射，如下所示：

public enum FinancialTransactionSortableField implements MappableEnum<FinancialTransactionSortableField>, SortableField {

  ID(DefaultSortableField.ID.getCode(), "Transaction Id", DefaultSortableField.ID.getColumnName()),
  CASH_AMOUNT("CashAmount", "Cash Amount", "cashAmount"),
  SECURITY_AMOUNT("SecurityAmount", "Security Amount", "securityAmount"),
  STATUS("Status", "Status", "status"),
  CREATED_TS(DefaultSortableField.CREATED_TS.getCode(),
             DefaultSortableField.CREATED_TS.getDescription(),
             DefaultSortableField.CREATED_TS.getColumnName()),;

  private final String code;
  private final String description;
  private final String columnName;

  private static final Map<String, FinancialTransactionSortableField> CODE_MAP =
    MappableEnumUtil.buildCodeMap(FinancialTransactionSortableField.class);

  private FinancialTransactionSortableField(final String code, final String description, final String columnName) {
    this.code = code;
    this.description = description;
    this.columnName = columnName;
  }

  @JsonValue
  @Override
  public String getCode() {
    return code;
  }

  @Override
  public String getDescription() {
    return description;
  }

  @Override
  public String getColumnName() {
    return columnName;
  }

  @Override
  public FinancialTransactionSortableField toEnum(final String code) {
    return fromCode(code);
  }

  @JsonCreator
  public static FinancialTransactionSortableField fromCode(final String code) {
    return CODE_MAP.get(code);
  }

}

3） 下面是

buildLookupMap

实现

public static <E extends Enum<E> & MappableEnum<E>> Map<String, E> buildLookupMap(
    final Class<E> enumClass, final EnumValueGetter<E> getter) {
    final Set<E> values = EnumSet.allOf(enumClass);
    final E enumValue = values.iterator().next();
    addToExampleMap(enumClass, enumValue);

    final Map<String, E> lookupMap = new LinkedHashMap<>(values.size());


    for (final E value : values) {
      final Set<String> keys = getter.getKeys(value);
      for (final String key : keys) {
        if (lookupMap.containsKey(key)) {
          throw new FPIllegalArgumentException("Lookup map for {} has duplicate key {}", enumClass.getSimpleName(), key);
        } else {
          lookupMap.put(key, value);
        }
      }
    }

    return lookupMap;
  }

而

EXAMPLE\u MAP

是一个在类开始时声明的映射，如下所示：

private static final Map<Class<?>, MappableEnum<?>> EXAMPLE_MAP =
    new ConcurrentHashMap<Class<?>, MappableEnum<?>>(1000);

私有静态最终映射>示例映射=
新ConcurrentHashMap>（1000）；

---

有人知道怎么了吗？如果需要更多信息，请告诉我。

好吧，如果

code\u MAP

中不存在

orderBy

的值，则MAP的get方法将返回null。@Evgeni但是，

行不应该返回code\u MAP.get（code）在这种情况下也将返回null，或者我在这里解释的是错误的吗？是的，它将是null。它有一个键，但有空value@janek您想让我粘贴
FinancialTransactionPaginationData
和'FinancialTransactionSortableField'的代码供您参考吗？您的问题可以完全归结为
buildCodeMap
的实现。如前所述，这不是Spring、Spring-4或Hibernate问题。请去掉那些标签。删除
LinkedHashMap
的源代码。删除
PaginationData
和
FinancialTransactionPaginationData
。仅在调用
fromCode
时保留非空参数值，即
enum
的实现。并添加
buildCodeMap
的实现。
 private static synchronized <E extends Enum<E> & MappableEnum<E>> void addToExampleMap(
    final Class<E> enumClass, final E enumValue) {
    if (!EXAMPLE_MAP.containsKey(enumClass)) {
      EXAMPLE_MAP.put(enumClass, enumValue);
    }
  } 

public static interface EnumValueGetter<E extends Enum<E> & MappableEnum<E>> {
    Set<String> getKeys(E e);
  }

private static final Map<Class<?>, MappableEnum<?>> EXAMPLE_MAP =
    new ConcurrentHashMap<Class<?>, MappableEnum<?>>(1000);