最近寫一個題目，要求將一組員工實體類轉換成xml文件，或將xml文件轉換成一組實體類。題目不難，但寫完感覺可以利用泛型和反射將任意一個實體類和xml文件進行轉換。于是今天下午立馬動手

試了下，做了個簡單的模型，可以將簡單的實體類和xml文件進行相互轉換，但對實體類的屬性類型有限制，目前只支持String, Integer, Double三種類型。但是后面可以擴展。

我的大概思路是這樣的，只要能拿到實體類的類型信息，我就能拿到實體類的全部字段名稱和類型，拼屬性的set和get方法更是簡單明了，這時候只需要通過方法的反射，將xml文件的數據讀取出來給這個反射即可。

反過來只要給我一個任意對象，我就能通過反射拿到該對象所有字段的值，這時候在寫xml文件即可。

具體代碼如下：

package com.pcq.entity;import java.io.*;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.DocumentHelper;import org.dom4j.Element;import org.dom4j.io.OutputFormat;import org.dom4j.io.SAXReader;import org.dom4j.io.XMLWriter;public class XMLAndEntityUtil { private static Document document = DocumentHelper.createDocument();  /**  * 判斷是否是個xml文件,目前類里尚未使用該方法  * @param filePath   * @return  */ @SuppressWarnings("unused") private static boolean isXMLFile(String filePath) {  File file = new File(filePath);  if(!file.exists() || filePath.indexOf(".xml") > -1) {   return false;  }  return true; }  /**  * 將一組對象數據轉換成XML文件  * @param list  * @param filePath 存放的文件路徑  */ public static <T> void writeXML(List<T> list, String filePath) {  Class<?> c = list.get(0).getClass();  String root = c.getSimpleName().toLowerCase() + "s";  Element rootEle = document.addElement(root);  for(Object obj : list) {   try {    Element e = writeXml(rootEle, obj);    document.setRootElement(e);    writeXml(document, filePath);   } catch (NoSuchMethodException | SecurityException     | IllegalAccessException | IllegalArgumentException     | InvocationTargetException e) {    e.printStackTrace();   }  } } /**  * 通過一個根節點來寫對象的xml節點，這個方法不對外開放，主要給writeXML(List<T> list, String filePath)提供服務  * @param root  * @param object  * @return  * @throws NoSuchMethodException  * @throws SecurityException  * @throws IllegalAccessException  * @throws IllegalArgumentException  * @throws InvocationTargetException  */ private static Element writeXml(Element root, Object object) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {  Class<?> c = object.getClass();  String className = c.getSimpleName().toLowerCase();  Element ele = root.addElement(className);  Field[] fields = c.getDeclaredFields();  for(Field f : fields) {   String fieldName = f.getName();   String param = fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);   Element fieldElement = ele.addElement(fieldName);   Method m = c.getMethod("get" + param, null);   String s = "";   if(m.invoke(object, null) != null) {    s = m.invoke(object, null).toString();   }   fieldElement.setText(s);  }  return root; }  /**  * 默認使用utf-8  * @param c  * @param filePath  * @return  * @throws UnsupportedEncodingException  * @throws FileNotFoundException  */ public static <T> List<T> getEntitys(Class<T> c, String filePath) throws UnsupportedEncodingException, FileNotFoundException {  return getEntitys(c, filePath, "utf-8"); } /**  * 將一個xml文件轉變成實體類  * @param c  * @param filePath  * @return  * @throws FileNotFoundException   * @throws UnsupportedEncodingException   */ public static <T> List<T> getEntitys(Class<T> c, String filePath, String encoding) throws UnsupportedEncodingException, FileNotFoundException {  File file = new File(filePath);  String labelName = c.getSimpleName().toLowerCase();  SAXReader reader = new SAXReader();  List<T> list = null;   try {   InputStreamReader in = new InputStreamReader(new FileInputStream(file), encoding);   Document document = reader.read(in);   Element root = document.getRootElement();   List elements = root.elements(labelName);   list = new ArrayList<T>();   for(Iterator<Emp> it = elements.iterator(); it.hasNext();) {     Element e = (Element)it.next();     T t = getEntity(c, e);     list.add(t);    }  } catch (DocumentException e) {   e.printStackTrace();  } catch (InstantiationException e1) {   e1.printStackTrace();  } catch (IllegalAccessException e1) {   e1.printStackTrace();  } catch (NoSuchMethodException e1) {   e1.printStackTrace();  } catch (SecurityException e1) {   e1.printStackTrace();  } catch (IllegalArgumentException e1) {   e1.printStackTrace();  } catch (InvocationTargetException e1) {   e1.printStackTrace();  }  return list; }   /**  * 將一種類型 和對應的 xml元素節點傳進來，返回該類型的對象,該方法不對外開放  * @param c 類類型  * @param ele 元素節點  * @return 該類型的對象  * @throws InstantiationException  * @throws IllegalAccessException  * @throws NoSuchMethodException  * @throws SecurityException  * @throws IllegalArgumentException  * @throws InvocationTargetException  */ @SuppressWarnings("unchecked") private static <T> T getEntity(Class<T> c, Element ele) throws InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {  Field[] fields = c.getDeclaredFields();  Object object = c.newInstance();//  for(Field f : fields) {   String type = f.getType().toString();//獲得字段的類型   String fieldName = f.getName();//獲得字段名稱   String param = fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);//把字段的第一個字母變成大寫   Element e = ele.element(fieldName);   if(type.indexOf("Integer") > -1) {//說明該字段是Integer類型    Integer i = null;    if(e.getTextTrim() != null && !e.getTextTrim().equals("")) {     i = Integer.parseInt(e.getTextTrim());    }    Method m = c.getMethod("set" + param, Integer.class);    m.invoke(object, i);//通過反射給該字段set值   }   if(type.indexOf("Double") > -1) { //說明該字段是Double類型    Double d = null;    if(e.getTextTrim() != null && !e.getTextTrim().equals("")) {     d = Double.parseDouble(e.getTextTrim());    }    Method m = c.getMethod("set" + param, Double.class);    m.invoke(object, d);   }   if(type.indexOf("String") > -1) {//說明該字段是String類型    String s = null;    if(e.getTextTrim() != null && !e.getTextTrim().equals("")) {     s = e.getTextTrim();    }    Method m = c.getMethod("set" + param, String.class);    m.invoke(object, s);   }  }  return (T)object; } /**  * 用來寫xml文件  * @param doc Document對象  * @param filePath 生成的文件路徑  * @param encoding 寫xml文件的編碼  */ public static void writeXml(Document doc, String filePath, String encoding) {  XMLWriter writer = null;  OutputFormat format = OutputFormat.createPrettyPrint();  format.setEncoding(encoding);// 指定XML編碼    try {   writer = new XMLWriter(new FileWriter(filePath), format);   writer.write(doc);  } catch (IOException e) {   e.printStackTrace();  } finally {   try {    writer.close();   } catch (IOException e) {    e.printStackTrace();   }  } }  /**  * 默認使用utf-8的格式寫文件  * @param doc  * @param filePath  */ public static void writeXml(Document doc, String filePath) {  writeXml(doc, filePath, "utf-8"); }}