Nous enregistrons généralement les paramètres de configuration des applications Java dans des fichiers de propriétés. Les fichiers de propriétés des applications Java peuvent être un fichier normal basé sur des paires clé-valeur avec des propriétés comme extension, ou il peut s'agir d'un fichier XML
.
Dans ce cas, nous présenterons comment générer des fichiers de propriétés dans ces deux formats via des programmes Java, et comment charger et utiliser ces deux fichiers de propriétés à partir du chemin de classe.
Voici le code du programme de cas :
PropertyFilesUtil.java
package com.journaldev.util;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.Set;
public class PropertyFilesUtil {
public static void main(String[] args) throws IOException {
String propertyFileName = "DB.properties";
String xmlFileName = "DB.xml";
writePropertyFile(propertyFileName, xmlFileName);
readPropertyFile(propertyFileName, xmlFileName);
readAllKeys(propertyFileName, xmlFileName);
readPropertyFileFromClasspath(propertyFileName);
} /**
* read property file from classpath
* @param propertyFileName
* @throws IOException
*/
private static void readPropertyFileFromClasspath(String propertyFileName) throws IOException {
Properties prop = new Properties();
prop.load(PropertyFilesUtil.class.getClassLoader().getResourceAsStream(propertyFileName));
System.out.println(propertyFileName +" loaded from Classpath::db.host = "+prop.getProperty("db.host"));
System.out.println(propertyFileName +" loaded from Classpath::db.user = "+prop.getProperty("db.user"));
System.out.println(propertyFileName +" loaded from Classpath::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(propertyFileName +" loaded from Classpath::XYZ = "+prop.getProperty("XYZ"));
} /**
* read all the keys from the given property files
* @param propertyFileName
* @param xmlFileName
* @throws IOException
*/
private static void readAllKeys(String propertyFileName, String xmlFileName) throws IOException {
System.out.println("Start of readAllKeys");
Properties prop = new Properties();
FileReader reader = new FileReader(propertyFileName);
prop.load(reader);
Set<Object> keys= prop.keySet(); for(Object obj : keys){
System.out.println(propertyFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
} //loading xml file now, first clear existing properties
prop.clear();
InputStream is = new FileInputStream(xmlFileName);
prop.loadFromXML(is);
keys= prop.keySet(); for(Object obj : keys){
System.out.println(xmlFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
} //Now free all the resources
is.close();
reader.close();
System.out.println("End of readAllKeys");
} /**
* This method reads property files from file system
* @param propertyFileName
* @param xmlFileName
* @throws IOException
* @throws FileNotFoundException
*/
private static void readPropertyFile(String propertyFileName, String xmlFileName) throws FileNotFoundException, IOException {
System.out.println("Start of readPropertyFile");
Properties prop = new Properties();
FileReader reader = new FileReader(propertyFileName);
prop.load(reader);
System.out.println(propertyFileName +"::db.host = "+prop.getProperty("db.host"));
System.out.println(propertyFileName +"::db.user = "+prop.getProperty("db.user"));
System.out.println(propertyFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(propertyFileName +"::XYZ = "+prop.getProperty("XYZ"));
//loading xml file now, first clear existing properties
prop.clear();
InputStream is = new FileInputStream(xmlFileName);
prop.loadFromXML(is);
System.out.println(xmlFileName +"::db.host = "+prop.getProperty("db.host"));
System.out.println(xmlFileName +"::db.user = "+prop.getProperty("db.user"));
System.out.println(xmlFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(xmlFileName +"::XYZ = "+prop.getProperty("XYZ"));
//Now free all the resources
is.close();
reader.close();
System.out.println("End of readPropertyFile");
} /**
* This method writes Property files into file system in property file
* and xml format
* @param fileName
* @throws IOException
*/
private static void writePropertyFile(String propertyFileName, String xmlFileName) throws IOException {
System.out.println("Start of writePropertyFile");
Properties prop = new Properties();
prop.setProperty("db.host", "localhost");
prop.setProperty("db.user", "user");
prop.setProperty("db.pwd", "password");
prop.store(new FileWriter(propertyFileName), "DB Config file");
System.out.println(propertyFileName + " written successfully");
prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");
System.out.println(xmlFileName + " written successfully");
System.out.println("End of writePropertyFile");
}
}Lorsque ce code est exécuté, la méthode writePropertyFile générera des fichiers de propriétés dans les deux formats ci-dessus et stockera les fichiers dans le projet sous le répertoire racine.
Les deux contenus du fichier de propriétés générés par la méthode writePropertyFile :
DB.properties
#DB Config file#Fri Nov 16 11:16:37 PST 2012db.user=user db.host=localhost db.pwd=password
DB.xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd"><properties><comment>DB Config XML file</comment> <entry key="db.user">user</entry><entry key="db.host">localhost</entry><entry key="db.pwd">password</entry> </properties>
Il est à noter que nous utilisons le élément de commentaire prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");Le deuxième paramètre de ce code est le contenu du commentaire. Si null est transmis, le fichier d'attributs XML généré n'aura aucun élément de commentaire.
Le résultat de la console est le suivant :
Start of writePropertyFile
DB.properties written successfully
DB.xml written successfully
End of writePropertyFile
Start of readPropertyFileDB.properties::db.host = localhostDB.properties::db.user =
userDB.properties::db.pwd = passwordDB.properties::XYZ = nullDB.xml::db.host =
localhostDB.xml::db.user = userDB.xml::db.pwd = passwordDB.xml::XYZ = null
End of readPropertyFile
Start of readAllKeysDB.properties:: Key=db.user::value=userDB.properties::
Key=db.host::value=localhostDB.properties:: Key=db.pwd::value=passwordDB.xml:: Key=db.user::value=userDB.xml::
Key=db.host::value=localhostDB.xml:: Key=db.pwd::value=password
End of readAllKeys
Exception in thread "main" java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Properties.java:434)
at java.util.Properties.load0(Properties.java:353)
at java.util.Properties.load(Properties.java:341)
at com.journaldev.util.PropertyFilesUtil.readPropertyFileFromClasspath(PropertyFilesUtil.java:31)
at com.journaldev.util.PropertyFilesUtil.main(PropertyFilesUtil.java:21)Une exception de pointeur nul est signalée ici. La raison est que le fichier généré est enregistré dans le répertoire racine du projet et est lu à partir du chemin de classe. . Copiez les deux fichiers de propriétés générés ci-dessus dans src et réexécutez le programme.
Nous enregistrons généralement les paramètres de configuration des applications Java dans des fichiers de propriétés. Les fichiers de propriétés des applications Java peuvent être un fichier normal basé sur des paires clé-valeur avec des propriétés comme extension, ou il peut s'agir d'un fichier XML. .
Dans ce cas, nous présenterons comment générer des fichiers de propriétés dans ces deux formats via des programmes Java, et comment charger et utiliser ces deux fichiers de propriétés à partir du chemin de classe.
Voici le code du programme de cas :
PropertyFilesUtil.java
package com.journaldev.util;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.Set;
public class PropertyFilesUtil {
public static void main(String[] args) throws IOException {
String propertyFileName = "DB.properties";
String xmlFileName = "DB.xml";
writePropertyFile(propertyFileName, xmlFileName);
readPropertyFile(propertyFileName, xmlFileName);
readAllKeys(propertyFileName, xmlFileName);
readPropertyFileFromClasspath(propertyFileName);
} /**
* read property file from classpath
* @param propertyFileName
* @throws IOException
*/
private static void readPropertyFileFromClasspath(String propertyFileName) throws IOException {
Properties prop = new Properties();
prop.load(PropertyFilesUtil.class.getClassLoader().getResourceAsStream(propertyFileName));
System.out.println(propertyFileName +" loaded from Classpath::db.host = "+prop.getProperty("db.host"));
System.out.println(propertyFileName +" loaded from Classpath::db.user = "+prop.getProperty("db.user"));
System.out.println(propertyFileName +" loaded from Classpath::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(propertyFileName +" loaded from Classpath::XYZ = "+prop.getProperty("XYZ"));
} /**
* read all the keys from the given property files
* @param propertyFileName
* @param xmlFileName
* @throws IOException
*/
private static void readAllKeys(String propertyFileName, String xmlFileName) throws IOException {
System.out.println("Start of readAllKeys");
Properties prop = new Properties();
FileReader reader = new FileReader(propertyFileName);
prop.load(reader);
Set<Object> keys= prop.keySet(); for(Object obj : keys){
System.out.println(propertyFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
} //loading xml file now, first clear existing properties
prop.clear();
InputStream is = new FileInputStream(xmlFileName);
prop.loadFromXML(is);
keys= prop.keySet(); for(Object obj : keys){
System.out.println(xmlFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
} //Now free all the resources
is.close();
reader.close();
System.out.println("End of readAllKeys");
} /**
* This method reads property files from file system
* @param propertyFileName
* @param xmlFileName
* @throws IOException
* @throws FileNotFoundException
*/
private static void readPropertyFile(String propertyFileName, String xmlFileName) throws FileNotFoundException, IOException {
System.out.println("Start of readPropertyFile");
Properties prop = new Properties();
FileReader reader = new FileReader(propertyFileName);
prop.load(reader);
System.out.println(propertyFileName +"::db.host = "+prop.getProperty("db.host"));
System.out.println(propertyFileName +"::db.user = "+prop.getProperty("db.user"));
System.out.println(propertyFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(propertyFileName +"::XYZ = "+prop.getProperty("XYZ"));
//loading xml file now, first clear existing properties
prop.clear();
InputStream is = new FileInputStream(xmlFileName);
prop.loadFromXML(is);
System.out.println(xmlFileName +"::db.host = "+prop.getProperty("db.host"));
System.out.println(xmlFileName +"::db.user = "+prop.getProperty("db.user"));
System.out.println(xmlFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
System.out.println(xmlFileName +"::XYZ = "+prop.getProperty("XYZ"));
//Now free all the resources
is.close();
reader.close();
System.out.println("End of readPropertyFile");
} /**
* This method writes Property files into file system in property file
* and xml format
* @param fileName
* @throws IOException
*/
private static void writePropertyFile(String propertyFileName, String xmlFileName) throws IOException {
System.out.println("Start of writePropertyFile");
Properties prop = new Properties();
prop.setProperty("db.host", "localhost");
prop.setProperty("db.user", "user");
prop.setProperty("db.pwd", "password");
prop.store(new FileWriter(propertyFileName), "DB Config file");
System.out.println(propertyFileName + " written successfully");
prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");
System.out.println(xmlFileName + " written successfully");
System.out.println("End of writePropertyFile");
}
}Lorsque ce code est exécuté, la méthode writePropertyFile générera des fichiers de propriétés dans les deux formats ci-dessus et stockera les fichiers dans le projet sous le répertoire racine.
Les deux contenus du fichier de propriétés générés par la méthode writePropertyFile :
DB.properties
#DB Config file#Fri Nov 16 11:16:37 PST 2012db.user=user db.host=localhost db.pwd=password
DB.xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE properties SYSTEM " <properties><comment>DB Config XML file</comment><entry key="db.user">user</entry><entry key="db.host">localhost</entry> <entry key="db.pwd">password</entry></properties>
Il est à noter que nous utilisons le élément de commentaire prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");Le deuxième paramètre de ce code est le contenu du commentaire. Si null est transmis, le fichier d'attributs XML généré n'aura aucun élément de commentaire.
Le contenu de la sortie de la console est le suivant :
Start of writePropertyFile
DB.properties written successfully
DB.xml written successfully
End of writePropertyFile
Start of readPropertyFileDB.properties::db.host = localhostDB.properties::db.user = userDB.properties::db.pwd = passwordDB.properties::XYZ =
nullDB.xml::db.host = localhostDB.xml::db.user = userDB.xml::db.pwd = passwordDB.xml::XYZ = null
End of readPropertyFile
Start of readAllKeysDB.properties:: Key=db.user::value=userDB.properties:: Key=db.host::value=localhostDB.properties:: Key=db.pwd::value=passwordDB.xml::
Key=db.user::value=userDB.xml:: Key=db.host::value=localhostDB.xml:: Key=db.pwd::value=password
End of readAllKeys
Exception in thread "main" java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Properties.java:434)
at java.util.Properties.load0(Properties.java:353)
at java.util.Properties.load(Properties.java:341)
at com.journaldev.util.PropertyFilesUtil.readPropertyFileFromClasspath(PropertyFilesUtil.java:31)
at com.journaldev.util.PropertyFilesUtil.main(PropertyFilesUtil.java:21)Ce qui précède est le contenu du didacticiel Java&Xml (10) XML en tant que fichier de propriétés. Pour plus de contenu connexe, veuillez faire attention au site Web PHP chinois. (www.php.cn) !
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