xml与java代码相互装换的工具类

这是一个java操作xml文件的工具类，最大的亮点在于能够通过工具类直接生成xml同样层次结构的java代码，也就是说，只要你定义好了xml的模板，就能一键生成java代码。省下了自己再使用工具类写代码的时间，极大得提高了效率。
首先来看看工具类代码

package com.lfq.createXml;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;

import org.apache.commons.lang3.StringUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**

操作xml文件以及生成java代码的工具
@author lfq
@since 1.0,Jun 12,2007
*/
public final class XmlUtils {

private static final String XMLNS_XSI = "xmlns:xsi";
private static final String XSI_SCHEMA_LOCATION = "xsi:schemaLocation";
private static final String LOGIC_YES = "yes";
private static final String DEFAULT_ENCODE = "UTF-8";
private static final String REG_INVALID_CHARS = "&#\d+;";

/**
- Creates a new document instance.
- @return a new document instance
- @throws XmlException problem creating a new document
  */
  public static Document newDocument() throws XmlException {
  Document doc = null;
  
  try {
  doc = DocumentBuilderFactory.newInstance().newDocumentBuilder()
  .newDocument();
  } catch (ParserConfigurationException e) {
  throw new XmlException(e);
  }
  
  return doc;
  }
/**
- Parses the content of the given XML file as an XML document.
- @param file the XML file instance
- @return the document instance representing the entire XML document
- @throws XmlException problem parsing the XML file
  */
  public static Document getDocument(File file) throws XmlException {
  InputStream in = getInputStream(file);
  return getDocument(in);
  }
/**
- Parses the content of the given stream as an XML document.
- @param in the XML file input stream
- @return the document instance representing the entire XML document
- @throws XmlException problem parsing the XML input stream
  */
  public static Document getDocument(InputStream in) throws XmlException {
  Document doc = null;
  
  try {
  DocumentBuilder builder = DocumentBuilderFactory.newInstance()
  .newDocumentBuilder();
  doc = builder.parse(in);
  } catch (ParserConfigurationException e) {
  throw new XmlException(e);
  } catch (SAXException e) {
  throw new XmlException(XmlException.XML_PARSE_ERROR,e);
  } catch (IOException e) {
  throw new XmlException(XmlException.XML_READ_ERROR,e);
  } finally {
  if (in != null) {
  try {
  in.close();
  } catch (IOException e) {
  // nothing to do
  }
  }
  }
  
  return doc;
  }
/**
- Creates a root element as well as a new document with specific tag name.
- @param tagName the name of the root element
- @return a new element instance
- @throws XmlException problem generating a new document
  */
  public static Element createRootElement(String tagName) throws XmlException {
  Document doc = newDocument();
  Element root = doc.createElement(tagName);
  doc.appendChild(root);
  return root;
  }
/**
- Gets the root element from input stream.
- @param in the XML file input stream
- @return the root element of parsed document
- @throws XmlException problem parsing the XML file input stream
  */
  public static Element getRootElementFromStream(InputStream in)
  throws XmlException {
  return getDocument(in).getDocumentElement();
  }
/**
- Gets the root element from given XML file.
- @param fileName the name of the XML file
- @return the root element of parsed document
- @throws XmlException problem parsing the XML file
  */
  public static Element getRootElementFromFile(File file)
  throws XmlException {
  return getDocument(file).getDocumentElement();
  }
/**
- Gets the root element from the given XML payload.
- @param payload the XML payload representing the XML file.
- @return the root element of parsed document
- @throws XmlException problem parsing the XML payload
  */
  public static Element getRootElementFromString(String payload)
  throws XmlException {
  if (payload == null || payload.trim().length() < 1) {
  throw new XmlException(XmlException.XML_PAYLOAD_EMPTY);
  }
  
  byte[] bytes = null;
  
  try {
  bytes = payload.getBytes(DEFAULT_ENCODE);
  } catch (UnsupportedEncodingException e) {
  throw new XmlException(XmlException.XML_ENCODE_ERROR,e);
  }
  
  InputStream in = new ByteArrayInputStream(bytes);
  return getDocument(in).getDocumentElement();
  }
/**
- Gets the descendant elements list from the parent element.
- @param parent the parent element in the element tree
- @param tagName the specified tag name
- @return the NOT NULL descendant elements list
  */
  public static List<Element> getElements(Element parent,String tagName) {
  NodeList nodes = parent.getElementsByTagName(tagName);
  List<Element> elements = new ArrayList<Element>();
  
  for (int i = 0; i < nodes.getLength(); i++) {
  Node node = nodes.item(i);
  if (node instanceof Element) {
  elements.add((Element) node);
  }
  }
  
  return elements;
  }
/**
- Gets the immediately descendant element from the parent element.
- @param parent the parent element in the element tree
- @param tagName the specified tag name.
- @return immediately descendant element of parent element,NULL otherwise.
  */
  public static Element getElement(Element parent,String tagName) {
  List<Element> children = getElements(parent,tagName);
  
  if (children.isEmpty()) {
  return null;
  } else {
  return children.get(0);
  }
  }
/**
- Gets the immediately child elements list from the parent element.
- @param parent the parent element in the element tree
- @param tagName the specified tag name
- @return the NOT NULL immediately child elements list
  */
  public static List<Element> getChildElements(Element parent,String tagName) {
  NodeList nodes = parent.getElementsByTagName(tagName);
  List<Element> elements = new ArrayList<Element>();
  
  for (int i = 0; i < nodes.getLength(); i++) {
  Node node = nodes.item(i);
  if (node instanceof Element && node.getParentNode() == parent) {
  elements.add((Element) node);
  }
  }
  
  return elements;
  }
/**
- Gets the immediately child element from the parent element.
- @param parent the parent element in the element tree
- @param tagName the specified tag name
- @return immediately child element of parent element,NULL otherwise
  */
  public static Element getChildElement(Element parent,String tagName) {
  List<Element> children = getChildElements(parent,tagName);
  
  if (children.isEmpty()) {
  return null;
  } else {
  return children.get(0);
  }
  }
/**
- Gets the value of the child element by tag name under the given parent
- element. If there is more than one child element,return the value of the
- first one.
- @param parent the parent element
- @param tagName the tag name of the child element
- @return value of the first child element,NULL if tag not exists
  */
  public static String getElementValue(Element parent,String tagName) {
  String value = null;
  
  Element element = getElement(parent,tagName);
  if (element != null) {
  value = element.getTextContent();
  }
  
  return value;
  }
/**
- Appends the child element to the parent element.
- @param parent the parent element
- @param tagName the child element name
- @return the child element added to the parent element
  */
  public static Element appendElement(Element parent,String tagName) {
  Element child = parent.getOwnerDocument().createElement(tagName);
  parent.appendChild(child);
  return child;
  }
/**
- Appends the child element as well as value to the parent element.
- @param parent the parent element
- @param tagName the child element name
- @param value the child element value
- @return the child element added to the parent element
  */
  public static Element appendElement(Element parent,String tagName,
  String value) {
  Element child = appendElement(parent,tagName);
  child.setTextContent(value);
  return child;
  }
/**
- Appends another element as a child element.
- @param parent the parent element
- @param child the child element to append
  */
  public static void appendElement(Element parent,Element child) {
  Node tmp = parent.getOwnerDocument().importNode(child,true);
  parent.appendChild(tmp);
  }
/**
- Appends the CDATA element to the parent element.
- @param parent the parent element
- @param tagName the CDATA element name
- @param value the CDATA element value
- @return the CDATA element added to the parent element
  */
  public static Element appendCDATAElement(Element parent,tagName);
  if (value == null) { // avoid "null" word in the XML payload
  value = "";
  }
  
  Node cdata = child.getOwnerDocument().createCDATASection(value);
  child.appendChild(cdata);
  return child;
  }
/**
- Converts the Node/Element instance to XML payload.
- @param node the node/element instance to convert
- @return the XML payload representing the node/element
- @throws XmlException problem converting XML to string
  */
  public static String childNodeToString(Node node) throws XmlException {
  String payload = null;
  
  try {
  Transformer tf = TransformerFactory.newInstance().newTransformer();
```
Properties props = tf.getOutputProperties();
props.setProperty(OutputKeys.OMIT_XML_DECLARATION,LOGIC_YES);
tf.setOutputProperties(props);

StringWriter writer = new StringWriter();
tf.transform(new DOMSource(node),new StreamResult(writer));
payload = writer.toString();
payload = payload.replaceAll(REG_INVALID_CHARS," ");
```
  } catch (TransformerException e) {
  throw new XmlException(XmlException.XML_TRANSFORM_ERROR,e);
  }
  
  return payload;
  }
/**
- Converts the Node/Document/Element instance to XML payload.
- @param node the node/document/element instance to convert
- @return the XML payload representing the node/document/element
- @throws XmlException problem converting XML to string
  */
  public static String nodeToString(Node node) throws XmlException {
  String payload = null;
  
  try {
  Transformer tf = TransformerFactory.newInstance().newTransformer();
```
Properties props = tf.getOutputProperties();
props.setProperty(OutputKeys.INDENT,LOGIC_YES);
props.setProperty(OutputKeys.ENCODING,DEFAULT_ENCODE);
tf.setOutputProperties(props);

StringWriter writer = new StringWriter();
tf.transform(new DOMSource(node),e);
}
 return payload;
}
 
```
/**
- Converts the an XML file to XML payload.
- @param file the XML file instance
- @return the XML payload representing the XML file
- @throws XmlException problem transforming XML to string
  */
  public static String xmlToString(File file) throws XmlException {
  Element root = getRootElementFromFile(file);
  return nodeToString(root);
  }
/**
- Converts the an XML file input stream to XML payload.
- @param in the XML file input stream
- @return the payload represents the XML file
- @throws XmlException problem transforming XML to string
  */
  public static String xmlToString(InputStream in) throws XmlException {
  Element root = getRootElementFromStream(in);
  return nodeToString(root);
  }
/**
- Saves the node/document/element as XML file.
- @param doc the XML node/document/element to save
- @param file the XML file to save
- @throws XmlException problem persisting XML file
  */
  public static void saveToXml(Node doc,File file) throws XmlException {
  OutputStream out = null;
  
  try {
  Transformer tf = TransformerFactory.newInstance().newTransformer();
```
Properties props = tf.getOutputProperties();
props.setProperty(OutputKeys.METHOD,XMLConstants.XML_NS_PREFIX);
props.setProperty(OutputKeys.INDENT,LOGIC_YES);
tf.setOutputProperties(props);

DOMSource dom = new DOMSource(doc);
out = getOutputStream(file);
Result result = new StreamResult(out);
tf.transform(dom,result);
```
  } catch (TransformerException e) {
  throw new XmlException(XmlException.XML_TRANSFORM_ERROR,e);
  } finally {
  if (out != null) {
  try {
  out.close();
  } catch (IOException e) {
  // nothing to do
  }
  }
  }
  }
/**
- Validates the element tree context via given XML schema file.
- @param doc the XML document to validate
- @param schemaFile the XML schema file instance
- @throws XmlException error occurs if the schema file not exists
  */
  public static void validateXml(Node doc,File schemaFile)
  throws XmlException {
  validateXml(doc,getInputStream(schemaFile));
  }
/**
- Validates the element tree context via given XML schema file.
- @param doc the XML document to validate
- @param schemaStream the XML schema file input stream
- @throws XmlException error occurs if validation fail
  */
  public static void validateXml(Node doc,InputStream schemaStream)
  throws XmlException {
  try {
  Source source = new StreamSource(schemaStream);
  Schema schema = SchemaFactory.newInstance(
  XMLConstants.W3C_XML_SCHEMA_NS_URI).newSchema(source);
```
Validator validator = schema.newValidator();
validator.validate(new DOMSource(doc));
```
  } catch (SAXException e) {
  throw new XmlException(XmlException.XML_VALIDATE_ERROR,e);
  } finally {
  if (schemaStream != null) {
  try {
  schemaStream.close();
  } catch (IOException e) {
  // nothing to do
  }
  }
  }
  }
/**
- Transforms the XML content to XHTML/HTML format string with the XSL.
- @param payload the XML payload to convert
- @param xsltFile the XML stylesheet file
- @return the transformed XHTML/HTML format string
- @throws XmlException problem converting XML to HTML
  */
  public static String xmlToHtml(String payload,File xsltFile)
  throws XmlException {
  String result = null;
  
  try {
  Source template = new StreamSource(xsltFile);
  Transformer transformer = TransformerFactory.newInstance()
  .newTransformer(template);
```
Properties props = transformer.getOutputProperties();
props.setProperty(OutputKeys.OMIT_XML_DECLARATION,LOGIC_YES);
transformer.setOutputProperties(props);

StreamSource source = new StreamSource(new StringReader(payload));
StreamResult sr = new StreamResult(new StringWriter());
transformer.transform(source,sr);

result = sr.getWriter().toString();
```
  } catch (TransformerException e) {
  throw new XmlException(XmlException.XML_TRANSFORM_ERROR,e);
  }
  
  return result;
  }
/**
- Sets the namespace to specific element.
- @param element the element to set
- @param namespace the namespace to set
- @param schemaLocation the XML schema file location URI
  */
  public static void setNamespace(Element element,String namespace,
  String schemaLocation) {
  element.setAttributeNS(XMLConstants.XMLNS_ATTRIBUTE_NS_URI,
  XMLConstants.XMLNS_ATTRIBUTE,namespace);
  element.setAttributeNS(XMLConstants.XMLNS_ATTRIBUTE_NS_URI,XMLNS_XSI,
  XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI);
  element.setAttributeNS(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI,
  XSI_SCHEMA_LOCATION,schemaLocation);
  }
/**
- Encode the XML payload to legality character.
- @param payload the XML payload to encode
- @return the encoded XML payload
- @throws XmlException problem encoding the XML payload
  */
  public static String encodeXml(String payload) throws XmlException {
  Element root = createRootElement(XMLConstants.XML_NS_PREFIX);
  root.setTextContent(payload);
  return childNodeToString(root.getFirstChild());
  }
private static InputStream getInputStream(File file) throws XmlException {
InputStream in = null;
```
try {
    in = new FileInputStream(file);
} catch (FileNotFoundException e) {
    throw new XmlException(XmlException.FILE_NOT_FOUND,e);
}

return in;
```
}

private static OutputStream getOutputStream(File file) throws XmlException {
OutputStream in = null;
```
try {
    in = new FileOutputStream(file);
} catch (FileNotFoundException e) {
    throw new XmlException(XmlException.FILE_NOT_FOUND,e);
}

return in;
```
}

/**
- @Desc 把实体类中有的字段直接转为xml节点
- @author LV_FQ
- @date 2016年12月15日
- @param parent
- @param formMap
- @param fields
  */
  public static void entityToXml(Element parent,String... fields){
  for(String field : fields){
  String temp = "XmlUtils.appendElement(root,\"" + field + "\",decHeadFormMap.getStr(\"field\"));";
  System.out.println(temp);
```
XmlUtils.appendElement(parent,field,"取值");
```
  }
  }
/**
- @Desc 根据xml生成java代码
- @author LV_FQ
- @date 2016年12月16日
- @param file xml文件
  */
  public static void createJavaCode(File file){
  XMLToJavaUtils.createJavaCode(file);
  }
  }

class XmlException extends RuntimeException {

private static final long serialVersionUID = 381260478228427716L;

public static final String XML_PAYLOAD_EMPTY = "xml.payload.empty";
public static final String XML_ENCODE_ERROR = "xml.encoding.invalid";
public static final String FILE_NOT_FOUND = "xml.file.not.found";
public static final String XML_PARSE_ERROR = "xml.parse.error";
public static final String XML_READ_ERROR = "xml.read.error";
public static final String XML_VALIDATE_ERROR = "xml.validate.error";
public static final String XML_TRANSFORM_ERROR = "xml.transform.error";

public XmlException() {
    super();
}

public XmlException(String key,Throwable cause) {
    super(key,cause);
}

public XmlException(String key) {
    super(key);
}

public XmlException(Throwable cause) {
    super(cause);
}

}

/**

@Desc 根据xml的格式生成xml的对应的java生成代码
@author LV_FQ
@date 2016年12月16日下午2:08:38
@version 1.0

*/
class XMLToJavaUtils {

public static void createJavaCode(File file) {
try {
//File file = new File("C:/Users/SUCCESS/Desktop/temp.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(file);
if (doc.hasChildNodes()) {
printNote(doc.getChildNodes(),null);
}
} catch (Exception e) {
e.printStackTrace();
}
}

private static void printNote(NodeList nodeList,Node parent) {
for (int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {

if(parent == null){
            System.out.println("Element "+ getTagName(node.getNodeName())+" = XmlUtils.createRootElement(\""+ node.getNodeName() +"\");");
        }else{
            String temp = "XmlUtils.appendElement("+getTagName(parent == null? null : parent.getNodeName())+",\"" + node.getNodeName();

            if (node.hasChildNodes() && node.getChildNodes().getLength() > 1) {
                System.out.println();
                //非叶节点把节点的名称加上，以便子节点和父节点做关联
                temp = "Element " + getTagName(node.getNodeName()) + " = " + temp + "\");";
            }else{
                //叶节点把注释加上
                //temp += "\",\"value\");//" + node.getTextContent();
                temp += "\",\""+ node.getTextContent() +"\");";
            }

            System.out.println(temp);
        }
        if (node.hasChildNodes()) {
            printNote(node.getChildNodes(),node);
        }
    }
}

}

/**

@Desc 把字符串第一个字母转小写
@author LV_FQ
@date 2016年12月16日
@param name
@return
*/
private static String getTagName(String name){
if(StringUtils.isBlank(name)){
return "";
}
String temp = name;
temp = temp.substring(0,1).toLowerCase() + temp.substring(1);
return temp;
}
}
测试类

package com.lfq.createXml;

import java.io.File;

import org.w3c.dom.Element;

public class TestXml {

public static void main(String[] args) {
    Element note = XmlUtils.createRootElement("note");
    XmlUtils.appendElement(note,"to","George1");
    XmlUtils.appendElement(note,"from","John2");
    XmlUtils.appendElement(note,"heading","Reminder1");
    XmlUtils.appendElement(note,"body","Don‘t forget the meeting!");

    XmlUtils.saveToXml(note,new File("/home/lv-success/Desktop/temp.xml"));

    //使用xml生成工具生成java代码(控制台输出)
    File file = new File("/home/lv-success/Desktop/temp.xml");
    XmlUtils.createJavaCode(file);
}

}
从test中可以看出，工具类通过已有的操作xml文件的方法读取xml的结构，同时根据读取的节点内容直接把对于生成的方法打印到控制台中，如此嵌套打印，最终打印出这个xml文件的相同java层次结构的代码。

如果对生成的java代码有不同要求，大家可以直接修改工具类中的生成java代码的方法。能生成自己最终要求最接近的代码最好，怎么方便怎么来哈。

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