Question

以下代码将永远获得nullPointerException，除非e.getKey()返回null

Map<Integer, Optional<SecurityAttributeChange>> spnCreationDetails;
Optional.ofNullable(spnCreationDetails.get(e.getKey()).orElse(new SecurityAttributeChange()).getNewAttribute())
                                    .orElse(new SecurityAttr())
                                    .getUserName());

我在这一行中正在使用NPE，是否可以调试它？我知道spnCreationDetails.get(e.getKey())返回null，在这里处理null时我错过了什么吗？

-编辑

这里是几乎完整的方法，它将帮助您提供有关如何重构它以便使其可读的输入。

private void updateAuditFields(List<SecurityAttributeChange> securityChanges, Map<Integer, Map<String, Object>> result) {

    Map<Integer, Optional<SecurityAttributeChange>> spnModificationDetails = ...

    Map<Integer, Optional<SecurityAttributeChange>> spnCreationDetails = ...

    result.entrySet().stream().forEach(e -> {
        e.getValue()
                .put("userIdLastChanged",
                        Optional.ofNullable(Optional.ofNullable(spnModificationDetails.get(e.getKey()))
                                .orElse(Optional.of(new SecurityAttributeChange()))
                                .get()
                                .getNewAttribute()).orElse(new SecurityAttr()).getUserName());

        e.getValue()
                .put("lastChangedDatetime",
                        Optional.ofNullable(Optional.ofNullable(spnModificationDetails.get(e.getKey()))
                                .orElse(Optional.of(new SecurityAttributeChange()))
                                .get()
                                .getNewAttribute()).orElse(new SecurityAttr()).getKnowledgeBeginDate());

        e.getValue()
                .put("userIdCreated", Optional.ofNullable(
                        Optional.ofNullable(spnCreationDetails.get(e.getKey())).orElse(Optional.of(new SecurityAttributeChange())).get().getNewAttribute())
                        .orElse(new SecurityAttr())
                        .getUserName());

        e.getValue()
                .put("createdDatetime",
                        Optional.ofNullable(Optional.ofNullable(spnCreationDetails.get(e.getKey()))
                                .orElse(Optional.of(new SecurityAttributeChange()))
                                .get()
                                .getNewAttribute()).orElse(new SecurityAttr()).getKnowledgeBeginDate());

    });
}

Answer 1

如果spnCreationDetails.get(e.getKey())为空，则可能需要：

Optional.ofNullable(spnCreationDetails.get(e.getKey()))
        .orElse(new SecurityAttributeChange())
        .getNewAttribute()
        .orElse(new SecurityAttr())
        .getUserName();

即spnCreationDetails.get(e.getKey())应该用Optional包装。

编辑：看到您的评论，spnCreationDetails.get(e.getKey())可以返回null或Optional<SecurityAttributeChange>，因此最好将null转换为新的{{ 1}}：

Optional

使用lamda时处理空指针

1 个答案: