[JAVA] [Problem solving] SAXReader: How to read an xml file with an external DTD file specified in an offline environment

environment

• org.dom4j.io.SAXReader

pom.xml

<dependency>
    <groupId>dom4j</groupId>
    <artifactId>dom4j</artifactId>
    <version>1.6.1</version>
</dependency>

<dependency>
    <groupId>jaxen</groupId>
    <artifactId>jaxen</artifactId>
    <version>1.1.1</version>
</dependency>

Thing you want to do

I want to read the following xml file with an external DTD file specified by ʻorg.dom4j.io.SAXReader`. However, I want to load it in an offline environment.

struts-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts-config PUBLIC
          "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN"
          "http://jakarta.apache.org/struts/dtds/struts-config_1_2.dtd">

<struts-config>
...
</struts-config>

problem

When I ran the following code in an offline environment, I got a ʻUnknownHostException`.

Bad.java

SAXReader reader = new SAXReader();
Document doc = reader.read("struts-config.xml");

Exception

org.dom4j.DocumentException: jakarta.apache.org Nested exception: jakarta.apache.org
	at org.dom4j.io.SAXReader.read(SAXReader.java:484)
	at org.dom4j.io.SAXReader.read(SAXReader.java:321)
	at test2.Test2.main(Test2.java:24)
Nested exception: 
java.net.UnknownHostException: jakarta.apache.org
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    ～～～

Cause

The cause is that the dtd file specified in the DOCTYPE declaration cannot be read. The solution was to not read the external DTD file.

Good.java

SAXReader reader = new SAXReader();
reader.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
Document doc = reader.read("struts-config.xml");

Reference site

https://xerces.apache.org/xerces2-j/features.html http://qiita.com/yoshi389111/items/3d0da72b1f2ccd947052 http://k-motohashi.hatenablog.com/entry/2013/04/24/115413