Jena 深入研究 之错误分析与OWL数据解析

2020-03-12   278 次阅读

Apache Jena不知道是我了解的少还是咋的，可能这个领域本身就比较冷门，网上的资料少之甚少，只能靠自己一点点摸索了

LiteralRequiredException

今天写bug的时候蹦出来一个新的错误
Exception in thread "main" org.apache.jena.rdf.model.LiteralRequiredException: http://www.daml.org/services/owl-s/1.1/Process.owl#Input
	at org.apache.jena.rdf.model.impl.StatementImpl.getLiteral(StatementImpl.java:113)

查阅Jena javadoc后得到如下英文

Exception to throw when an RDFNode required to be a Literal isn't, or when a literal Node is required but a non-literal Node supplied.

结合我出错的语句
System.out.println("statement.getLiteral():"+statement.getLiteral());
可以看出getLinteral()这个函数要求满足条件是对应的Statement对象是Literal类型的，而本次调用的statement的类型如下所示
statement.getClass():class org.apache.jena.rdf.model.impl.StatementImpl
很明显并不是Literal类型
最后再放上getLiteral()函数的定义

getLiteral
Literal getLiteral()
Return the object of the statement. 
An exception will be thrown if the object is not a Literal.
Returns:
The Literal which is the object of the statement.

有类似问题的函数还有

  • getBoolean()
  • getByte()
  • getShort()
  • getLong()
  • getChar()
  • getFloat()
  • getString()
  • getInt()
  • getLanguage()

getSubject() , getPredicate(), getObject()

学过英语的人应该对这三个词语不陌生
Subject即主语，Predicate即谓语, Object即宾语
我们都知道三元组
形式其实和主谓宾结构类似
因此这三个函数就是从statement中抽取“主语”，“谓语”和“宾语”
Nt数据statement

[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#平均负荷, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Input]

定义三个不同类型变量如下

Resource subject=statement.getSubject();
Property property=statement.getPredicate();
RDFNode objectNode=statement.getObject();

分别输出三个变量.toString()如下

Resource:file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#平均负荷 
Property:http://www.w3.org/1999/02/22-rdf-syntax-ns#type 
object:http://www.daml.org/services/owl-s/1.1/Process.owl#Input

解析OWL文件

本次解析OWL文件来自以下地址
数据来源
首先将OWL数据存放在.owl文件中
1.jpg
还真够多的
随后进入eclipse开始撸代码

  1. 创建模型
    Model model3 = ModelFactory.createDefaultModel();
  2. 读取程序
    是一个返回模型的函数
    在函数体中创建模型Model
    随后创建输入流
    InputStream inputStream = FileManager.get().open(FileName);
    然后直接使用Model类型的read方法即可,返回模型
    完整代码

Model FileRead(String FileName)
	{
		Model model2 = ModelFactory.createDefaultModel();
		InputStream inputStream = FileManager.get().open(FileName);
		if(inputStream==null) {
			throw new IllegalArgumentException("File"+inputStream+"not found");
		}
		
		model2.read(inputStream,null);
		return model2;
	}

至此该文件中的内容已经被读取到所建立的模型中了
接下来就是测试读取效果
3. 输出函数

StmtIterator list = model3.listStatements(null,null,(RDFNode)null);
		while(list.hasNext())
			System.out.println(list.next());

建立Statement迭代器list,随后直接输出,结果如下

[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最低负荷, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Input]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最高负荷, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Input]
[2e9ea962-4d4f-4ade-b11a-79aa937cc93f, http://www.daml.org/services/owl-s/1.1/Process.owl#process, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess]
[2e9ea962-4d4f-4ade-b11a-79aa937cc93f, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Perform]
[c8f03d9b-cab1-4f53-b619-1210272964f3, http://www.daml.org/services/owl-s/1.1/Process.owl#components, cfb2c7df-a47b-43d9-aa1a-968d9c67305c]
[c8f03d9b-cab1-4f53-b619-1210272964f3, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Sequence]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Process.owl#hasOutput, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#负荷预警信息]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Process.owl#composedOf, c8f03d9b-cab1-4f53-b619-1210272964f3]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Process.owl#hasInput, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最低负荷]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Process.owl#hasInput, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最高负荷]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Service.owl#describes, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadService]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.daml.org/services/owl-s/1.1/Process.owl#hasResult, 93bb8120-b7db-41d3-8c9a-f32d7c62073e]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProcess, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#CompositeProcess]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProfile, http://www.daml.org/services/owl-s/1.1/Profile.owl#textDescription, "Composite Service"]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProfile, http://www.daml.org/services/owl-s/1.1/Service.owl#presentedBy, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadService]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProfile, http://www.daml.org/services/owl-s/1.1/Profile.owl#hasInput, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最高负荷]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProfile, http://www.daml.org/services/owl-s/1.1/Profile.owl#hasInput, file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最低负荷]
[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#PayloadProfile, http://www.w3.org/2000/01/rdf-schema#label, "Composite Service"]

数据解析成功
随后可以用上面提到的三个提取主谓宾的方法来提取信息

statement:[file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最高负荷, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.daml.org/services/owl-s/1.1/Process.owl#Input]
ResourceParse
Resource:file:/D:/WorkSpace/CreateOWL-SFile/ontologyFiles/jiaxidianli1.owl#最高负荷 
Property:http://www.w3.org/1999/02/22-rdf-syntax-ns#type 
object:http://www.daml.org/services/owl-s/1.1/Process.owl#Input
statement.getClass():class org.apache.jena.rdf.model.impl.StatementImpl

注意

在执行函数
StmtIterator list = model3.listStatements(null,null,(RDFNode)null);
第三个参数处的null务必要强制类型转换成RDFNode，否则会报编译错误

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
	The method listStatements(Resource, Property, RDFNode) is ambiguous for the type Model

Q.E.D.

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