[JAVA] Try reading XML with JDOM

What is DOM

A convenient library for reading XML. Click here for a detailed overview (https://qiita.com/bocc/items/5d7213431e5a5e3a67e9)

It runs under Spring MVC, so it's not versatile at all. I don't know such a special environment! People please go here

For Spring users It seems that Spring IO manages dependencies, so let's use it immediately.

Add library to Maven

pom.xml

	<!-- JDOM -->
	<dependency>
	    <groupId>org.jdom</groupId>
	    <artifactId>jdom2</artifactId>
	</dependency>

As always, version control is Spring IO.

Try reading XML.

Assuming a web service (although it doesn't have to be) Let's read the XML.

This is the XML used for the sample

sample.xml

<?xml version="1.0" encoding="UTF-8"?>
<employees>
	<employee>
		<name>Yamamoto</name>
		<class>Sales Section1</class>
		<sex>male</sex>
		<age>10</age>
	</employee>

	<employee>
		<name>Hanako</name>
		<class>Sales Section2</class>
		<sex>female</sex>
		<age>20</age>
	</employee>
	
		<employee>
		<name>Taniguchi</name>
		<class>Develop Section2</class>
		<sex>male</sex>
		<age>30</age>
	</employee>

</employees>

Let's get this in ** src / main / resource **.

DomController.java

	@Autowired
	ResourceLoader resourceLoader;
	
	@RequestMapping(value="/readable")
	public String readable() {
		
		//File acquisition
		Resource resource = resourceLoader.getResource("classpath:sample.xml");
		
		Document doc = null;
		Element root = null;
		
		//Get Xml
		try {
			doc = new SAXBuilder().build(resource.getFile());
			root = doc.getRootElement();
			
			} catch (JDOMException e) {
				System.out.println(e);
			} catch (IOException e) {
				//TODO auto-generated catch block
				System.out.println(e);
			}

From now on, the Spring code will be mixed. If it is a normal sample, ** resource.getFile () ** will be ** new File ("hogehoge.xml") **

What you are doing

DomController.java

			doc = new SAXBuilder().build(resource.getFile());
			root = doc.getRootElement();

I'm just getting the root element here.

Try to get a child element

DomController.java

		//Get child elements from Xml (not grandchild elements)
		List<Element> list = root.getChildren();

This time there are 3 child elements, so it will be a List.

Try to get the value of the grandchild element.

Try to get the value of name under employee. You can also get the value of the attribute by changing ** getValue () ** to ** getAttribute ("hoge_name") **. The number of loops increases as the number of grandchildren and great-grandchildren increases. (I think it's a technique for searching for "trees" from around here.)

DomController.java

		List<String> result = new ArrayList<String>();
		
		//Loop to get grandchild element from Xml
		for(Element e : list) {
			if(e.getName().compareTo("employee") == 0) {
				result.add(e.getChild("name").getValue());
			}
		}
		
		//Loop to spit out the retrieved element to the console
		for(String name : result) {
			System.out.println(name);
		}

This is the final completed system

DomController.java

@RestController
public class DomController {

	@Autowired
	ResourceLoader resourceLoader;
	
	@RequestMapping(value="/readable")
	public String readable() {
		
		//File acquisition
		Resource resource = resourceLoader.getResource("classpath:sample.xml");
		
		Document doc = null;
		Element root = null;
		
		//Get Xml
		try {
			doc = new SAXBuilder().build(resource.getFile());
			root = doc.getRootElement();
			
			} catch (JDOMException e) {
				System.out.println(e);
			} catch (IOException e) {
				//TODO auto-generated catch block
				System.out.println(e);
			}
	
		//Get child elements from Xml (not grandchild elements)
		List<Element> list = root.getChildren();
		
		List<String> result = new ArrayList<String>();
		
		//Loop to get grandchild element from Xml
		for(Element e : list) {
			if(e.getName().compareTo("employee") == 0) {
				result.add(e.getChild("name").getValue());
			}
		}
		
		//Loop to spit out the retrieved element to the console
		for(String name : result) {
			System.out.println(name);
		}
	
        return null;
	}

There is no problem with @Controller even if it is not @RestController.

Try to move

Let's access it from a browser and check the operation.

Console screen

You can see that the value of name is obtained from XML.