eugenp · eric-martin · May 13, 2025 · Apr 28, 2025 · Apr 28, 2025 · Apr 29, 2025
diff --git a/core-java-modules/core-java-properties/pom.xml b/core-java-modules/core-java-properties/pom.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-properties</artifactId>
     <version>0.1.0-SNAPSHOT</version>
@@ -14,4 +14,21 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-</project>
+    <properties>
+        <apache.commons.version>2.11.0</apache.commons.version>
+        <commons.beanutils.version>1.10.1</commons.beanutils.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-configuration2</artifactId>
+            <version>${apache.commons.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-beanutils</groupId>
+            <artifactId>commons-beanutils</artifactId>
+            <version>${commons.beanutils.version}</version>
+        </dependency>
+    </dependencies>
+</project>
diff --git a/...perties/src/main/java/com/baeldung/core/java/properties/ApacheCommonsPropertyMutator.java b/...perties/src/main/java/com/baeldung/core/java/properties/ApacheCommonsPropertyMutator.java
@@ -0,0 +1,41 @@
+package com.baeldung.core.java.properties;
+
+import org.apache.commons.configuration2.Configuration;
+import org.apache.commons.configuration2.FileBasedConfiguration;
+import org.apache.commons.configuration2.PropertiesConfiguration;
+import org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder;
+import org.apache.commons.configuration2.builder.fluent.Parameters;
+import org.apache.commons.configuration2.ex.ConfigurationException;
+
+public class ApacheCommonsPropertyMutator implements PropertyMutator {
+
+    private final String propertyFileName;
+
+    public ApacheCommonsPropertyMutator(String propertyFileName) {
+        this.propertyFileName = propertyFileName;
+    }
+
+    @Override
+    public String getProperty(String key) throws ConfigurationException {
+        FileBasedConfigurationBuilder<FileBasedConfiguration> builder = getAppPropertiesConfigBuilder();
+        Configuration properties = builder.getConfiguration();
+
+        return (String) properties.getProperty(key);
+    }
+
+    @Override
+    public void addOrUpdateProperty(String key, String value) throws ConfigurationException {
+        FileBasedConfigurationBuilder<FileBasedConfiguration> builder = getAppPropertiesConfigBuilder();
+        Configuration configuration = builder.getConfiguration();
+
+        configuration.setProperty(key, value);
+        builder.save();
+    }
+
+    private FileBasedConfigurationBuilder<FileBasedConfiguration> getAppPropertiesConfigBuilder() {
+        Parameters params = new Parameters();
+
+        return new FileBasedConfigurationBuilder<FileBasedConfiguration>(PropertiesConfiguration.class).configure(params.properties()
+          .setFileName(propertyFileName));
+    }
+}
diff --git a/...va-properties/src/main/java/com/baeldung/core/java/properties/FileAPIPropertyMutator.java b/...va-properties/src/main/java/com/baeldung/core/java/properties/FileAPIPropertyMutator.java
@@ -0,0 +1,78 @@
+package com.baeldung.core.java.properties;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+
+public class FileAPIPropertyMutator {
+
+    private final String propertyFileName;
+    private final PropertyLoader propertyLoader;
+
+    public FileAPIPropertyMutator(String propertyFileName, PropertyLoader propertyLoader) {
+        this.propertyFileName = propertyFileName;
+        this.propertyLoader = propertyLoader;
+    }
+
+    public String getPropertyKeyWithValue(int lineNumber) throws IOException {
+        List<String> fileLines = getFileLines();
+        // depending on the system, sometimes the first line will be a comment with a timestamp of the file read
+        // the next line will make this method compatible with all systems
+        if (fileLines.get(0).startsWith("#")) {
+            lineNumber++;
+        }
+
+        return fileLines.get(lineNumber);
+    }
+
+    public String getLastPropertyKeyWithValue() throws IOException {
+        List<String> fileLines = getFileLines();
+
+        return fileLines.get(fileLines.size() - 1);
+    }
+
+    public void addPropertyKeyWithValue(String keyAndValue) throws IOException {
+        File propertiesFile = new File(propertyLoader.getFilePathFromResources(propertyFileName));
+        List<String> fileContent = getFileLines(propertiesFile);
+
+        fileContent.add(keyAndValue);
+        Files.write(propertiesFile.toPath(), fileContent, StandardCharsets.UTF_8);
+    }
+
+    public int updateProperty(String oldKeyValuePair, String newKeyValuePair) throws IOException {
+        File propertiesFile = new File(propertyLoader.getFilePathFromResources(propertyFileName));
+        List<String> fileContent = getFileLines(propertiesFile);
+        int updatedIndex = -1;
+
+        for (int i = 0; i < fileContent.size(); i++) {
+            if (fileContent.get(i)
+              .replaceAll("\\s+", "")
+              .equals(oldKeyValuePair)) {
+                fileContent.set(i, newKeyValuePair);
+                updatedIndex = i;
+                break;
+            }
+        }
+        Files.write(propertiesFile.toPath(), fileContent, StandardCharsets.UTF_8);
+
+        // depending on the system, sometimes the first line will be a comment with a timestamp of the file read
+        // the next line will make this method compatible with all systems
+        if (fileContent.get(0).startsWith("#")) {
+            updatedIndex--;
+        }
+
+        return updatedIndex;
+    }
+
+    private List<String> getFileLines() throws IOException {
+        File propertiesFile = new File(propertyLoader.getFilePathFromResources(propertyFileName));
+        return getFileLines(propertiesFile);
+    }
+
+    private List<String> getFileLines(File propertiesFile) throws IOException {
+        return new ArrayList<>(Files.readAllLines(propertiesFile.toPath(), StandardCharsets.UTF_8));
+    }
+}
diff --git a/...roperties/src/main/java/com/baeldung/core/java/properties/FileStreamsPropertyMutator.java b/...roperties/src/main/java/com/baeldung/core/java/properties/FileStreamsPropertyMutator.java
@@ -0,0 +1,33 @@
+package com.baeldung.core.java.properties;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Properties;
+
+public class FileStreamsPropertyMutator implements PropertyMutator {
+
+    private final String propertyFileName;
+    private final PropertyLoader propertyLoader;
+
+    public FileStreamsPropertyMutator(String propertyFileName, PropertyLoader propertyLoader) {
+        this.propertyFileName = propertyFileName;
+        this.propertyLoader = propertyLoader;
+    }
+
+    @Override
+    public String getProperty(String key) throws IOException {
+        Properties properties = propertyLoader.fromFile(propertyFileName);
+
+        return properties.getProperty(key);
+    }
+
+    @Override
+    public void addOrUpdateProperty(String key, String value) throws IOException {
+        Properties properties = propertyLoader.fromFile(propertyFileName);
+        properties.setProperty(key, value);
+
+        FileOutputStream out = new FileOutputStream(propertyLoader.getFilePathFromResources(propertyFileName));
+        properties.store(out, null);
+        out.close();
+    }
+}
diff --git a/.../core-java-properties/src/main/java/com/baeldung/core/java/properties/PropertyLoader.java b/.../core-java-properties/src/main/java/com/baeldung/core/java/properties/PropertyLoader.java
@@ -0,0 +1,29 @@
+package com.baeldung.core.java.properties;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.URL;
+import java.util.Objects;
+import java.util.Properties;
+
+public class PropertyLoader {
+
+    public Properties fromFile(String filename) throws IOException {
+        String appPropertiesFileName = getFilePathFromResources(filename);
+        FileInputStream in = new FileInputStream(appPropertiesFileName);
+        Properties properties = new Properties();
+
+        properties.load(in);
+        in.close();
+
+        return properties;
+    }
+
+    public String getFilePathFromResources(String filename) {
+        URL resourceUrl = getClass().getClassLoader()
+          .getResource(filename);
+        Objects.requireNonNull(resourceUrl, "Property file with name [" + filename + "] was not found.");
+
+        return resourceUrl.getFile();
+    }
+}
diff --git a/...core-java-properties/src/main/java/com/baeldung/core/java/properties/PropertyMutator.java b/...core-java-properties/src/main/java/com/baeldung/core/java/properties/PropertyMutator.java
@@ -0,0 +1,12 @@
+package com.baeldung.core.java.properties;
+
+import java.io.IOException;
+
+import org.apache.commons.configuration2.ex.ConfigurationException;
+
+public interface PropertyMutator {
+
+    String getProperty(String key) throws IOException, ConfigurationException;
+
+    void addOrUpdateProperty(String key, String value) throws IOException, ConfigurationException;
+}
diff --git a/...va-properties/src/main/java/com/baeldung/core/java/properties/XMLFilePropertyMutator.java b/...va-properties/src/main/java/com/baeldung/core/java/properties/XMLFilePropertyMutator.java
@@ -0,0 +1,58 @@
+package com.baeldung.core.java.properties;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Objects;
+import java.util.Properties;
+
+public class XMLFilePropertyMutator implements PropertyMutator {
+
+    private final String propertyFileName;
+
+    public XMLFilePropertyMutator(String propertyFileName) {
+        this.propertyFileName = propertyFileName;
+    }
+
+    @Override
+    public String getProperty(String key) throws IOException {
+        Properties properties = loadProperties();
+
+        return properties.getProperty(key);
+    }
+
+    @Override
+    public void addOrUpdateProperty(String key, String value) throws IOException {
+        String filePath = getXMLAppPropertiesWithFileStreamFilePath();
+        Properties properties = loadProperties(filePath);
+
+        try (OutputStream os = Files.newOutputStream(Paths.get(filePath))) {
+            properties.setProperty(key, value);
+            properties.storeToXML(os, null);
+        }
+    }
+
+    private Properties loadProperties() throws IOException {
+        return loadProperties(getXMLAppPropertiesWithFileStreamFilePath());
+    }
+
+    private Properties loadProperties(String filepath) throws IOException {
+        Properties props = new Properties();
+        try (InputStream is = Files.newInputStream(Paths.get(filepath))) {
+            props.loadFromXML(is);
+        }
+
+        return props;
+    }
+
+    String getXMLAppPropertiesWithFileStreamFilePath() {
+        URL resourceUrl = getClass().getClassLoader()
+          .getResource(propertyFileName);
+        Objects.requireNonNull(resourceUrl, "Property file with name [" + propertyFileName + "] was not found.");
+
+        return resourceUrl.getFile();
+    }
+}
diff --git a/...src/test/java/com/baeldung/core/java/properties/ApacheCommonsPropertyMutatorUnitTest.java b/...src/test/java/com/baeldung/core/java/properties/ApacheCommonsPropertyMutatorUnitTest.java
@@ -0,0 +1,56 @@
+package com.baeldung.core.java.properties;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Properties;
+
+import org.apache.commons.configuration2.ex.ConfigurationException;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class ApacheCommonsPropertyMutatorUnitTest {
+
+    private static final String PROPERTY_FILE_NAME = "app.properties";
+    private final PropertyLoader propertyLoader = new PropertyLoader();
+    private Properties initialProperties;
+
+    private final ApacheCommonsPropertyMutator propertyMutator = new ApacheCommonsPropertyMutator(PROPERTY_FILE_NAME);
+
+    @BeforeEach
+    public void loadInitialPropertiesFromFile() throws IOException {
+        initialProperties = propertyLoader.fromFile(PROPERTY_FILE_NAME);
+    }
+
+    @AfterEach
+    public void restoreInitialPropertiesToFile() throws IOException {
+        FileOutputStream out = new FileOutputStream(propertyLoader.getFilePathFromResources(PROPERTY_FILE_NAME));
+        initialProperties.store(out, null);
+        out.close();
+    }
+
+    @Test
+    public void givenApacheCommons_whenAddNonExistingProperty_thenNewPropertyWithoutAffectingOtherProperties() throws ConfigurationException {
+        assertNull(propertyMutator.getProperty("new.property"));
+        assertEquals("TestApp", propertyMutator.getProperty("name"));
+
+        propertyMutator.addOrUpdateProperty("new.property", "new-value");
+
+        assertEquals("new-value", propertyMutator.getProperty("new.property"));
+        assertEquals("TestApp", propertyMutator.getProperty("name"));
+    }
+
+    @Test
+    public void givenApacheCommons_whenUpdateExistingProperty_thenUpdatedPropertyWithoutAffectingOtherProperties() throws ConfigurationException {
+        assertEquals("1.0", propertyMutator.getProperty("version"));
+        assertEquals("TestApp", propertyMutator.getProperty("name"));
+
+        propertyMutator.addOrUpdateProperty("version", "2.0");
+
+        assertEquals("2.0", propertyMutator.getProperty("version"));
+        assertEquals("TestApp", propertyMutator.getProperty("name"));
+    }
+}