处理protobuffers中的空值 [英] Handling null values in protobuffers

问题描述

我正在研究从数据库中获取数据并构造protobuff消息的东西。鉴于可以从数据库中为某些字段提取空值，我将在尝试构建protobuff消息时获得Null指针异常。通过线程 http：//来支持protobuffs不支持null code.google.com/p/protobuf/issues/detail?id=57 ，我想知道处理NPE的唯一其他方法是将手动检查插入到与原型对应的java文件中，如下所示！

I am working on something which fetches data from database and constructs protobuff message. Given the possibility that null values can be fetched from the database for certain fields , I will get Null-pointer exception while trying to construct the protobuff message. Getting to know that null is not supported in protobuffs from the thread http://code.google.com/p/protobuf/issues/detail?id=57, I am wondering whether the only other way to handle NPE getting thrown is to insert manual checks into the java file corresponding to the proto like below!

message ProtoPerson{
    optional string firstName = 1;
    optional string lastName = 2;
    optional string address1 = 3;
}

ProtoPerson.Builder builder = ProtoPerson.Builder.newBuilder();
if (p.getFirstName() != null) builder.setFirstName(p.getFirstName());
if (p.getLastName() != null) builder.setLastName(p.getLastName());
if (p.getAddress1() != null) builder.setAddress1(p.getAddress1());
...

所以有人可以澄清是否还有其他可行的有效方法在protobuff构造期间处理空值??

So can someone please clarify whether there is any other possible efficient way to handle the null values during protobuff construction??

推荐答案

对此没有简单的解决方案。我建议只处理空检查。但如果你真的想摆脱它们，这里有几个想法：

There's no easy solution to this. I'd recommend just dealing with the null checks. But if you really want to get rid of them, here are a couple ideas:

• 你可以写一个代码生成器插件，添加 setOrClearFoo （）每个Java类的方法。 Java代码生成器为此提供插入点（请参阅该页面的结尾）。


• 您可以使用Java反射来迭代 get *（） <$ c $的方法c> p ，调用每一个，检查 null ，然后调用 set *（） 方法如果非null。这将具有额外的优势，即每次添加新字段时都不必更新复制代码，但它比编写明确复制每个字段的代码要慢得多。

• You could write a code generator plugin which adds setOrClearFoo() methods to each Java class. The Java code generator provides insertion points for this (see the end of that page).
• You could use Java reflection to iterate over the get*() methods of p, call each one, check for null, and then call the set*() method of builder if non-null. This will have the added advantage that you won't have to update your copy code every time you add a new field, but it will be much slower than writing code that copies each field explicitly.

这篇关于处理protobuffers中的空值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！