为什么DOM文档在实际有效时显示为null？

本文介绍了为什么DOM文档在实际有效时显示为null？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在我的一种方法中，我有一个实例化的DOM org.w3c.dom.Document ，似乎被正确初始化，因为当我使用以下方式转储它时：

In one of my methods I have a DOM org.w3c.dom.Document instantiated and seems to be initialized properly since when I dump it using:

LOG.info("DOM: " + doc.getDocumentElement().getTextContent());

它输出应该存在的SOAP消息的有效和最新内容。

It outputs a valid and current content of a SOAP message that should be there.

但是之前（和之后）只有一个声明，它显示为 null ：

But only one statement before (and after), it shows as null:

LOG.info("doc BEFORE = " + doc); LOG.info("DOM: " + doc.getDocumentElement().getTextContent()); LOG.info("doc AFTER: = " + doc);

他们都显示 null ，总共

They both show null with totally valid content in between.

这对我没有意义...我还缺少什么？

This doesn't make sense to me... What am I missing?

根据意见中的建议更新，我将日志语句更改为

Update, per the suggestions in the comments: I changed the log statements to

LOG.info("doc BEFORE/AFTER = " + doc + ", " + doc.toString() + ", " + (doc==null));

输出为：

INFO：doc BEFORE = [#document：null]，[#document：null]，false

INFO: doc BEFORE = [#document: null], [#document: null], false

因此，@qqilihq是正确的：该文档不为空，但doc.toString（）是。

I therefore conclude that @qqilihq is right: The doc is not null, but doc.toString() is.

推荐答案

qqilihq有正确的想法。做一个 System.out.println（doc.getClass（））; ，然后google实现文档它打印出来。找到源代码后，查找 toString（）方法。我会打赌它只是返回 null 。

I bet @qqilihq has the right idea. Do a System.out.println(doc.getClass());, then google the source code of the class implementing Document that it prints out. Once you find the source code, look for the toString() method. I would bet it's just returning null.