簡單實體類和xml檔案的相互轉換，實體xml相互轉換

簡單實體類和xml檔案的相互轉換，實體xml相互轉換

最近寫一個題目，要求將一組員工實體類轉換成xml檔案，或將xml檔案轉換成一組實體類。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檔案進行轉換。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檔案進行相互轉換，但對實體類的屬性類型有限制，目前只支援String, Integer, Double三種類型。但是後面可以擴充。

我的大概思路是這樣的，只要能拿到實體類的類型資訊，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檔案的資料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檔案即可。

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檔案,目前類裡尚未使用該方法     * @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;    }        /**     * 將一組對象資料轉換成XML檔案     * @param list     * @param filePath 存放的檔案路徑     */    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;    }        /**     * 預設使用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檔案轉變成實體類     * @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檔案     * @param doc Document對象     * @param filePath 產生的檔案路徑     * @param encoding 寫xml檔案的編碼     */    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();            }        }    }        /**     * 預設使用utf-8的格式寫檔案     * @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檔案格式如下：

<?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檔案如下

<?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檔案，才能轉換成實體類，要求是實體類的類類型資訊（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,可以看到工具類裡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。