最近写一个题目，要求将一组员工实体类转换成xml文件，或将xml文件转换成一组实体类。题目不难，但写完感觉可以利用泛型和反射将任意一个实体类和xml文件进行转换。于是今天下午立马动手
试了下，做了个简单的模型，可以将简单的实体类和xml文件进行相互转换，但对实体类的属性类型有限制，目前只支持String, Integer, Double三种类型。但是后面可以扩展。
我的大概思路是这样的，只要能拿到实体类的类型信息，我就能拿到实体类的全部字段名称和类型，拼属性的set和get方法更是简单明了，这时候只需要通过方法的反射，将xml文件的数据读取出来给这个反射即可。
反过来只要给我一个任意对象，我就能通过反射拿到该对象所有字段的值，这时候在写xml文件即可。
具体代码如下：
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(); /** * 判断是否是个xml文件,目前类里尚未使用该方法 * @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; } /** * 将一组对象数据转换成XML文件 * @param list * @param filePath 存放的文件路径 */ 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(); } } } /** * 通过一个根节点来写对象的xml节点，这个方法不对外开放，主要给writeXML(List<T> list, String filePath)提供服务 * @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; } /** * 默认使用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"); } /** * 将一个xml文件转变成实体类 * @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; } /** * 将一种类型 和对应的 xml元素节点传进来，返回该类型的对象,该方法不对外开放 * @param c 类类型 * @param ele 元素节点 * @return 该类型的对象 * @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();//获得字段的类型 String fieldName = f.getName();//获得字段名称 String param = fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);//把字段的第一个字母变成大写 Element e = ele.element(fieldName); if(type.indexOf("Integer") > -1) {//说明该字段是Integer类型 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);//通过反射给该字段set值 } if(type.indexOf("Double") > -1) { //说明该字段是Double类型 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) {//说明该字段是String类型 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; } /** * 用来写xml文件 * @param doc Document对象 * @param filePath 生成的文件路径 * @param encoding 写xml文件的编码 */ public static void writeXml(Document doc, String filePath, String encoding) { XMLWriter writer = null; OutputFormat format = OutputFormat.createPrettyPrint(); format.setEncoding(encoding);// 指定XML编码 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(); } } } /** * 默认使用utf-8的格式写文件 * @param doc * @param filePath */ public static void writeXml(Document doc, String filePath) { writeXml(doc, filePath, "utf-8"); } }
假如有个实体类是：