Save objects with Java XMLEncoder

Java XMLEncoderto save the object,XMLDecoderRestore with

Javaobject with theXML formatHere is a sample program that saves in
For XML output, use theXMLEncoderto be used.
andXMLDecoderA sample program to restore a saved object is also presented at the same time using

sample program

• Fields declared private are preserved when Getter and Setter methods are defined.
• Only if there is a change in a variable, it is saved in an XML file.
• HashMap, java.util.ArrayList, etc. can also be specified as objects to be saved. ArrayList, etc. This is useful for storing the state of objects in a simple manner.

/**<br /> * java.beans.XMLEncoderを使用し、オブジェクト[object]を、<br /> * 指定したパス[path]に、XMLファイルとして保存します。<br /> * ※オブジェクト[object]がJavaBeansの慣例に適合している場合、<br /> * 　プライベートなフィールドのデータも保存できます。<br /> * ※保存したXMLファイルはjava.beans.XMLDecoderで復元する事ができます。<br /> * @param path オブジェクトを保存するパス。<br /> * 存在しない場合可能であれば作成します。<br /> * @param object 保存するオブジェクト。<br /> * @throws FileNotFoundException<br /> * 指定されたパス名で示されるファイルが開けなかった場合<br /> */<br /> public static synchronized void writeXML(String path, Object object)<br /> throws IOException {<br /> XMLEncoder enc = null;<br /> ByteArrayOutputStream out = new ByteArrayOutputStream();<br /> FileOutputStream fileStream = null;<br /> try {<br /> // 先にメモリ中にXMLデータを出力する<br /> enc = new XMLEncoder(out);<br /> enc.writeObject(object);<br /> enc.close(); // close()の中でflush()が呼ばれる。<br /> byte[] xmlbuff = out.toByteArray();</p> <p> // Output byte data to file<br /> fileStream = new FileOutputStream(path);<br /> fileStream.write(xmlbuff);<br /> fileStream.flush();<br /> } finally {<br /> if (enc != null) {<br /> enc.close();<br /> }<br /> if (out != null) {<br /> out.close();<br /> }<br /> if (fileStream != null) {<br /> fileStream.close();<br /> }<br /> }<br /> }<br /> /**<br /> * Restores the object from the XML file at the specified path [path].<br /> * *XML files must be saved using java.beans.XMLEncoder.<br /> * @param path The path where the object is stored.<br /> * @throws FileNotFoundException<br /> * If the file indicated by the specified path name does not exist<br /> */<br /> public static Object readXML(String path) throws FileNotFoundException {<br /> XMLDecoder d = null;<br /> try {<br /> d = new XMLDecoder(new BufferedInputStream(<br /> new FileInputStream(path)));<br /> return d.readObject();<br /> } finally {<br /> if (d != null) {<br /> d.close();<br /> }<br /> }<br /> }<br />

*The following class is used as a sample of a class to be saved.
public class FreeSoft {<br /> private String name;<br /> private String url;<br /> public String getName() {<br /> return name;<br /> }<br /> public void setName(String name) {<br /> this.name = name;<br /> }<br /> public String getUrl() {<br /> return url;<br /> }<br /> public void setUrl(String url) {<br /> this.url = url;<br /> }<br /> }<br />

Execution Result

◆Example of Execution
public static void main(String[] args) {<br /> try {<br /> // FreeSoftクラスのインスタンスを生成しXMLに出力<br /> FreeSoft freeSoft = new FreeSoft();<br /> freeSoft.setName(“Chat＆Messenger チャットもメッセンジャーも！！”);<br /> freeSoft.setUrl(“https://chat-messenger.com/”);<br /> writeXML(“C:\\FreeSoft.xml”,freeSoft); </p> <p> // Restore instance of FreeSoft class from XML<br /> FreeSoft freeSoft2 = (FreeSoft)readXML(“C:\\FreeSoft.xml”);<br /> System.out.println(“Soft name:”+freeSoft2.getName());<br /> System.out.println(“URL:”+freeSoft2.getUrl());<br /> } catch (Exception e) {<br /> e.printStackTrace();<br /> }<br /> }<br />
◆Output result

Software name: Chat & Messenger Chat and Messenger!
URL: https://chat-messenger.com/

◆C:\FreeSoft.xml contents

Points to keep in mind when using this service

XMLEncoder and java.beans.XMLDecoder classes, but in practical use with Chat&Messenger, we have confirmed that in extremely rare cases, when outputting to XML with java.beans. XMLEncoder.
ParseException is logged to "Standard Error Output" when a 0-byte file is read.

The reason for this is that the file becomes empty when the FileOutputStream instance is created.
I believe it occurs when the Java process is shut down after instantiating the FileOutputStream but before outputting the XML data.

Chat&Messenger has created backup files to work around this problem.