To use the DOM parser to read XML files, you can use the DocumentBuilder class under the javax.xml.parsers package in the Java Standard library. The following are the steps to read an XML file using a DOM parser: 1. Create a DocumentBuilderFactory object, which is used to obtain an instance of the DOM parser. 2. Call the newDocumentBuilder() method of DocumentBuilderFactory to create a DocumentBuilder object. 3. Use the parse() method of the DocumentBuilder object to parse the XML file and convert it into a Document object. 4. Through the Document object, elements and attributes in XML files can be obtained, and then operations can be performed on XML files. The following is an example of Java code that reads an XML file using a DOM parser: ```java import org.w3c.dom.*; import javax.xml.parsers.*; public class DOMParserExample { public static void main(String[] args) throws Exception { //Create a DocumentBuilderFactory object DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); //Create a DocumentBuilder object DocumentBuilder builder = factory.newDocumentBuilder(); //Parsing XML files using DocumentBuilder objects to obtain Document objects Document document = builder.parse("example.xml"); //Get the root element of the XML file Element rootElement = document.getDocumentElement(); //Obtain sub elements under the root element NodeList nodeList = rootElement.getChildNodes(); //Traverse sub elements for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Element) { Element element = (Element) node; //Obtain the tag name of the element String tagName = element.getTagName(); //Get the text content of the element String textContent = element.getTextContent(); System.out.println("Tag Name: " + tagName); System.out.println("Text Content: " + textContent); } } } } ``` The example XML file (example.xml) used in the above code is as follows: ```xml <?xml version="1.0" encoding="UTF-8"?> <root> <item>Item 1</item> <item>Item 2</item> <item>Item 3</item> </root> ``` Before using this code, it is necessary to ensure that the following Maven dependencies are added to the pom.xml file of the project: ```xml <dependencies> <dependency> <groupId>javax.xml.parsers</groupId> <artifactId>jaxp-api</artifactId> <version>1.4.2</version> </dependency> </dependencies> ``` This way, you can use the DOM parser to read the XML file.

To use the SAX parser to read XML files, you can use Java's built-in 'javax. xml. parsers. SAXParser' class and 'org. xml. sax. helpers. DefaultHandler' class. These classes can be operated by using the Java Standard library without any third-party library. The following is the Java sample code: Firstly, you need to create a custom handler class that implements the 'ContentHandler' interface to handle events in XML files. ```java import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; public class MyHandler extends DefaultHandler { //Mark the name of the currently processed element private String currentElement; //Processing Element Start Event @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { //Mark current element currentElement = qName; } //Handle element end event @Override public void endElement(String uri, String localName, String qName) throws SAXException { //Reset current element tags currentElement = null; } //Handling element content events @Override public void characters(char[] ch, int start, int length) throws SAXException { if (currentElement != null) { //Process element content, such as printing to the console System.out.println("Element: " + currentElement + ", Text: " + new String(ch, start, length)); } } } ``` In this handler, we override the 'startElement', 'endElement', and 'characters' methods to handle different events in XML files, such as element start, element end, and element content events. Next, you can use the SAX parser for file parsing. ```java import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import java.io.File; public class Main { public static void main(String[] args) { try { //Create SAXParser factory instance SAXParserFactory factory = SAXParserFactory.newInstance(); //Create SAXParser instance SAXParser parser = factory.newSAXParser(); //Create a custom handler instance MyHandler handler = new MyHandler(); //Parsing XML files parser.parse(new File("example.xml"), handler); } catch (Exception e) { e.printStackTrace(); } } } ``` In this example, we first create an instance of 'SAXParserFactory', and then use that factory instance to create an instance of 'SAXParser'. Next, we create a custom handler instance and pass it to the 'parse' method. Finally, the parser will automatically call the methods of the handler to handle the events in the XML file. The above is a basic example, and you can extend and modify the processing program and parsing logic according to your own needs. Please ensure to replace 'example. xml' with the actual XML file path.

In Java, you can use XPath expressions to query XML nodes and return information such as node collections and attributes. Java provides the javax. xml. xpath package to support XPath queries. The following is an example code for querying and returning a node set using XPath: Firstly, the following Maven dependencies need to be added: ```xml <dependency> <groupId>javax.xml</groupId> <artifactId>javax.xml-api</artifactId> <version>1.0.1</version> </dependency> ``` Next, let's assume the following XML example: ```xml <root> <element attribute="attributeValue1">value1</element> <element attribute="attributeValue2">value2</element> <element attribute="attributeValue3">value3</element> </root> ``` Then, you can use the following Java code to query and return the node set using XPath: ```java import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.xpath.*; import org.w3c.dom.Document; import org.w3c.dom.NodeList; public class XPathExample { public static void main(String[] args) throws Exception { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document document = builder.parse("path/to/xml/file.xml"); XPathFactory xpathFactory = XPathFactory.newInstance(); XPath xpath = xpathFactory.newXPath(); //Query Node Collection XPathExpression expr = xpath.compile("//element"); NodeList nodeList = (NodeList) expr.evaluate(document, XPathConstants.NODESET); //Traverse the node set, merge and print node and attribute values for (int i = 0; i < nodeList.getLength(); i++) { String value = nodeList.item(i).getTextContent(); String attribute = nodeList.item(i).getAttributes().getNamedItem("attribute").getNodeValue(); System.out.println("Value: " + value + ", Attribute: " + attribute); } } } ``` In the above code, the XPath expression "//element" is used to query the collection of nodes named "element" in the XML document. In the code, we call the evaluate method of XPath and specify the XPathConstants. NODESET parameter to obtain the node set. Then, traverse the node set and use the getAttributes and getNamedItem methods to obtain the attribute values and node values of the node. It should be noted that the 'path/to/xml/file. xml' in the code should be replaced with the actual XML file path. I hope it can help you!

Transforming XML files into HTML or other formats using XSLT expressions in Java can be achieved through the following steps: 1. Import Dependency: Add the following Maven dependencies to the pom.xml file (you can also manually download the jar file to import the project): ```xml <dependency> <groupId>javax.xml</groupId> <artifactId>jaxp-api</artifactId> <version>1.4.5</version> </dependency> ``` 2. Create an XSLT converter: Create a TransformerFactory object using the TransformerFactory class in the javax. xml. transform package, and then use this object to create a Transformer object. TransformerFactory is Thread safety, so it can be reused throughout the application. ```java import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; TransformerFactory factory = TransformerFactory.newInstance(); Transformer transformer = factory.newTransformer(); ``` 3. Define an XSLT stylesheet: Create an XSLT stylesheet file that contains conversion rules for converting XML into HTML or other formats. The following is a simple example of an XSLT-style representation that converts the name element in XML into an HTML h1 title: ```xml <!-- test.xslt --> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <html> <head> <title>XML to HTML Conversion</title> </head> <body> <h1> <xsl:value-of select="name"/> </h1> </body> </html> </xsl:template> </xsl:stylesheet> ``` 4. Perform conversion: Use the Transformer object to convert the XML file to an XSLT stylesheet file, and save the results to the target file. ```java import javax.xml.transform.Source; import javax.xml.transform.Result; import javax.xml.transform.stream.StreamSource; import javax.xml.transform.stream.StreamResult; import java.io.File; File xmlFile = new File("input.xml"); File xsltFile = new File("test.xslt"); File outputFile = new File("output.html"); Source xmlSource = new StreamSource(xmlFile); Source xsltSource = new StreamSource(xsltFile); Result outputResult = new StreamResult(outputFile); transformer.transform(xmlSource, outputResult); ``` The above code assumes an input XML file called "input. xml", which contains a name element. The converted results will be saved in an HTML file called "output. html". It should be noted that the above example code is only a simple demonstration. If you need to handle more complex XML and XSLT transformations, please refer to relevant documents and tutorials.

To read an XML file and obtain a Document object using a JDOM parser, follow the following steps: 1. Add Maven dependency: Add the following dependency relationships in the pom.xml file of the project: ```xml <dependency> <groupId>org.jdom</groupId> <artifactId>jdom2</artifactId> <version>2.0.6</version> </dependency> ``` 2. Create an XML sample file: Assuming we have an XML file called "example. xml", the content is as follows: ```xml <?xml version="1.0" encoding="UTF-8"?> <root> <element1>Hello</element1> <element2>World</element2> <element3> <subelement>Example</subelement> </element3> </root> ``` 3. Use the JDOM parser to read the XML file and obtain the Document object: ```java import org.jdom2.Document; import org.jdom2.Element; import org.jdom2.input.SAXBuilder; import java.io.File; public class JDOMExample { public static void main(String[] args) { try { File file = new File("example.xml"); SAXBuilder saxBuilder = new SAXBuilder(); Document document = saxBuilder.build(file); Element rootElement = document.getRootElement(); System.out.println("Root element name: " + rootElement.getName()); Element element1 = rootElement.getChild("element1"); System.out.println("element1 value: " + element1.getValue()); Element element3 = rootElement.getChild("element3"); Element subElement = element3.getChild("subelement"); System.out.println("subelement value: " + subElement.getValue()); } catch (Exception e) { e.printStackTrace(); } } } ``` The above code first specifies the XML file to be parsed through the File object, and then creates a new XML parser using SAXBuilder. Next, call the 'saxBuilder. build (file)' method to parse the file and return a Document object. By using the Document object, we can obtain the root element, child element, and print their values. Note that this example is only a simple demonstration, and if more complex XML operations are required, more detailed code may be required.

To test the content comparison between XML files using XML Unit, you can use the XML Unit library. You can include XML Unit by adding the following dependencies in the Maven project: ```xml <dependency> <groupId>org.xmlunit</groupId> <artifactId>xmlunit-core</artifactId> <version>2.8.2</version> <scope>test</scope> </dependency> ``` The following is a Java example code that compares two XML files using XML Unit: ```java import org.xmlunit.builder.DiffBuilder; import org.xmlunit.diff.Diff; import org.xmlunit.diff.Difference; import org.xmlunit.diff.DifferenceEvaluator; import org.xmlunit.util.Nodes; public class XMLComparison { public static void main(String[] args) { String expectedXML = "<root><element1>value1</element1></root>"; String actualXML = "<root><element1>value2</element1></root>"; Diff xmlDiff = DiffBuilder.compare(expectedXML) .withTest(actualXML) .build(); if (xmlDiff.hasDifferences()) { System.out.println("XML files are not identical."); for (Difference difference : xmlDiff.getDifferences()) { System.out.println("Difference: " + difference.getDescription()); //Get Differences Node System.out.println("Expected: " + Nodes.getNodeAsString(difference.getComparison().getControlDetails().getTarget())); System.out.println("Actual: " + Nodes.getNodeAsString(difference.getComparison().getTestDetails().getTarget())); } } else { System.out.println("XML files are identical."); } } } ``` In the above example code, we pass' expectedXML 'and' actualXML 'as strings to the' DiffBuilder. compare() 'method. Then, we check for any differences using the 'xmlDiff. hasDifferences()' method. If there are differences, we can use the 'xmlDiff. getDifferences()' method to obtain all the differences, and use the 'Nodes. getNodeAsString()' method to obtain the string representation of the difference nodes. Finally, we can handle the differences as needed. Please note that the above example code assumes that the root node of two XML files is'<root>'and only contains one child element'<element1>'. Here is an example of 'expectedXML' and 'actualXML': ```xml <!-- expectedXML --> <root> <element1>value1</element1> </root> <!-- actualXML --> <root> <element1>value2</element1> </root> ``` I hope this can help you start using XML Unit for XML file comparison.

To use XML Beans to achieve mutual conversion between XML and Java objects, you can follow the following steps: 1. Add XML Beans Maven dependency: ```xml <dependency> <groupId>org.apache.xmlbeans</groupId> <artifactId>xmlbeans</artifactId> <version>3.1.0</version> </dependency> ``` 2. Create an XML Schema file (XSD file) for defining XML structures and validating XML documents. For example, create an XSD file called "person. xsd" and define a "person" element that contains "name" and "age" attributes: ```xml <?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="person"> <xs:complexType> <xs:sequence> <xs:element name="name" type="xs:string"/> <xs:element name="age" type="xs:int"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> ``` 3. Use the XMLBeans command line tool (xmlbeans-3.1.0. jar) to compile the XSD file into a Java class file. Open the command line terminal and execute the following command: ``` java -jar xmlbeans-3.1.0.jar person.xsd ``` The above commands will generate Java class file named "PersonDocument. java" and "PersonType. java". 4. In Java code, use the XML Beans API to read and manipulate XML documents. The following is an example code that parses an XML document containing a "person" element and converts it into a Java object: ```java import org.apache.xmlbeans.*; import com.example.PersonDocument; public class Main { public static void main(String[] args) throws XmlException { //Load an XML document from an XML file XmlObject xmlObject = XmlObject.Factory.parse("person.xml"); //Convert an XML document into a PersonDocument object PersonDocument personDoc = PersonDocument.Factory.parse(xmlObject); //Get Person Object PersonType person = personDoc.getPerson(); //Accessing and manipulating properties of Person objects System.out.println("Name: " + person.getName()); System.out.println("Age: " + person.getAge()); } } ``` In the example code, "person. xml" is an XML file containing the "person" element: ```xml <person> <name>John Doe</name> <age>30</age> </person> ``` Note: In practical use, relevant code adjustments should be made based on one's own XML structure and needs.

To use the API of the Apache POI or JExcel API library to read Excel files, you first need to add the corresponding dependencies in the project. Using the Apache POI library: Maven Dependency: ```xml <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi</artifactId> <version>4.1.0</version> </dependency> <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi-ooxml</artifactId> <version>4.1.0</version> </dependency> ``` Excel example: Suppose there is a worksheet named "Sheet1" in the Excel file, which contains two columns of data: name and age. |Name | Age| |------|------| |Zhang San | 20| |Li Si | 25| |Wang Wu | 30| Java sample code: ```java import org.apache.poi.ss.usermodel.*; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import java.io.File; import java.io.FileInputStream; import java.io.InputStream; public class ReadExcelWithPOI { public static void main(String[] args) { try { //Open Excel file InputStream inputStream = new FileInputStream(new File("path/to/excel_file.xlsx")); Workbook workbook = new XSSFWorkbook(inputStream); //Get Worksheet Sheet sheet = workbook.getSheet("Sheet1"); //Traversal row for (Row row : sheet) { //Read Cell Data Cell cell1 = row.getCell(0); String name = cell1.getStringCellValue(); Cell cell2 = row.getCell(1); double age = cell2.getNumericCellValue(); //Print Data System. out. println ("Name:"+name+", Age:"+(int) age); } //Close Stream inputStream.close(); workbook.close(); } catch (Exception e) { e.printStackTrace(); } } } ``` Using the JExcelAPI library: Maven Dependency: ```xml <dependency> <groupId>net.sourceforge.jexcelapi</groupId> <artifactId>jxl</artifactId> <version>2.6.12</version> </dependency> ``` The Excel sample and Java sample code are used in the same way as the Apache POI library. Simply change the imported class name and some API call methods to the corresponding classes and methods of the JExcel API.

You can create Excel files using the API of the Apache POI library. Firstly, you need to add Apache POI dependencies to the pom.xml file of the project: ```xml <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi</artifactId> <version>4.1.2</version> </dependency> <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi-ooxml</artifactId> <version>4.1.2</version> </dependency> ``` Next, you can use the following example code to create an Excel file with two columns of data: ```java import org.apache.poi.ss.usermodel.*; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import java.io.FileOutputStream; import java.io.IOException; public class ExcelCreator { public static void main(String[] args) throws IOException { //Create Workbook Workbook workbook = new XSSFWorkbook(); //Create a worksheet Sheet sheet = workbook.createSheet("Sheet1"); //Create header Row headerRow = sheet.createRow(0); Cell headerCell1 = headerRow.createCell(0); headerCell1.setCellValue("Name"); Cell headerCell2 = headerRow.createCell(1); headerCell2.setCellValue("Age"); //Create Data Rows Row dataRow = sheet.createRow(1); Cell dataCell1 = dataRow.createCell(0); dataCell1.setCellValue("Alice"); Cell dataCell2 = dataRow.createCell(1); dataCell2.setCellValue(25); //Create file output stream FileOutputStream fileOutputStream = new FileOutputStream("example.xlsx"); //Write Workbook to Output Stream workbook.write(fileOutputStream); //Close output stream fileOutputStream.close(); //Close Workbook workbook.close(); } } ``` This sample code will create an Excel file with two columns of data, the first column being Name and the second column being Age, with the data line Alice (25 years old). Finally, the file will be saved as a file named example.xlsx.

To insert and delete cell objects using the XSSFRow class, you need to first create an XSSFWorkbook object and load an Excel file, then obtain the corresponding table sheet and row row. Firstly, before using the XSSFRow class for insertion and deletion, it is necessary to add the Apache POI dependency in the pom.xml file: ```xml <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi-ooxml</artifactId> <version>4.1.2</version> </dependency> ``` Next, let's assume we have an Excel file called "example. xlsx", which contains a table called "Sheet1". In this table, we have the following data: |A | B | C| |-------|------|------| |1 | 2 | 3| |4 | 5 | 6| |7 | 8 | 9| Prepare another sample Java code: ```java import org.apache.poi.ss.usermodel.*; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.util.Iterator; public class ExcelManipulation { public static void main(String[] args) { try { //Load Excel file FileInputStream file = new FileInputStream("example.xlsx"); Workbook workbook = new XSSFWorkbook(file); //Obtain the table sheet (assuming we choose the first sheet) Sheet sheet = workbook.getSheetAt(0); //Insert Cells InsertCell (sheet, 1, 1, "10")// Insert a cell with a value of 10 in the second row and second column //Delete Cells DeleteCell (sheet, 2, 2)// Delete cells from row 3 and column 3 //Save the modified Excel file FileOutputStream outFile = new FileOutputStream("example.xlsx"); workbook.write(outFile); //Close file stream outFile.close(); file.close(); } catch (IOException e) { e.printStackTrace(); } } //Insert Cells public static void insertCell(Sheet sheet, int rowNum, int colNum, String value) { Row row = sheet.getRow(rowNum); if (row == null) { row = sheet.createRow(rowNum); } Cell cell = row.createCell(colNum); cell.setCellValue(value); } //Delete Cells public static void deleteCell(Sheet sheet, int rowNum, int colNum) { Row row = sheet.getRow(rowNum); if (row != null) { Cell cell = row.getCell(colNum); if (cell != null) { row.removeCell(cell); } } } } ``` In this example, we loaded an Excel file called "example. xlsx", inserted a cell with a value of 10 on the first sheet, and deleted the cells in the third row and third column. Finally, we save the modified Excel file. Please note that the Excel file path here is relative to the directory where the Java code is located. The key to the entire process is to use classes provided by Apache POI such as XSSFWorkbook, Sheet, Row, and Cell to manipulate cells in Excel files.