簡單實體類轉換成xml文件

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。於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。但是後面可以擴展。

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欄位名稱和類型，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欄位的值，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();//獲得欄位的類型

String fieldName = f.getName();//獲得欄位名稱

String param = fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);//把欄位的第一個字母變成大寫

Element e = ele.element(fieldName);

if(type.indexOf("Integer") > -1) {//說明該欄位是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);//通過反射給該欄位set值

}

if(type.indexOf("Double") > -1) { //說明該欄位是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) {//說明該欄位是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");

}

}

假如有個實體類是：

package com.pcq.entity;

import java.io.Serializable;

public class Emp implements Serializable{

private Integer id;

private String name;

private Integer deptNo;

private Integer age;

private String gender;

private Integer bossId;

private Double salary;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Integer getDeptNo() {

return deptNo;

}

public void setDeptNo(Integer deptNo) {

this.deptNo = deptNo;

}

public Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

public String getGender() {

return gender;

}

public void setGender(String gender) {

this.gender = gender;

}

public Integer getBossId() {

return bossId;

}

public void setBossId(Integer bossId) {

this.bossId = bossId;

}

public Double getSalary() {

return salary;

}

public void setSalary(Double salary) {

this.salary = salary;

}

}

那麼寫出來的xml文件格式如下：

<?xml version="1.0" encoding="utf-8"?>

<emps>

<emp>

<id>1</id>

<name>張三</name>

<deptNo>50</deptNo>

<age>25</age>

<gender>男</gender>

<bossId>6</bossId>

<salary>9000.0</salary>

</emp>

<emp>

<id>2</id>

<name>李四</name>

<deptNo>50</deptNo>

<age>22</age>

<gender>女</gender>

<bossId>6</bossId>

<salary>8000.0</salary>

</emp>

</emps>

假如有個實體類如下：

package com.pcq.entity;

public class Student {

private Integer id;

private String name;

private Integer age;

private String gender;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

public String getGender() {

return gender;

}

public void setGender(String gender) {

this.gender = gender;

}

}

那麼寫出來的xml文件如下

<?xml version="1.0" encoding="utf-8"?>

<students>

<student>

<id></id>

<name>pcq</name>

<age>18</age>

<gender>男</gender>

</student>

</students>

讀取也必須讀這種格式的xml文件，才能轉換成實體類，要求是實體類的類類型信息（Class）必須要獲得到。

另外這裡的實體類的屬性類型均是Integer,String,Double,可以看到工具類里只對這三種類型做了判斷。而且可以預想的是，如果出現一對多的關係，即一個實體類擁有一組另一個類對象的引用，

那xml和實體類的相互轉換要比上述的情況複雜的多。lz表示短時間內甚至長時間內也不一定能做的出來，歡迎同道高人指點。

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