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BAEL-7617: Intro to Apache Commons Configuration (#16281)
* BAEL-7617: Intro to Apache Commons Configuration * BAEL-7617: Review Comments * BAEL-7617: Review Comments * BAEL-7617: Review Comments
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‎libraries-apache-commons-2/pom.xml

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<version>${mockftpserver.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-configuration2</artifactId>
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<version>${commons-configuration2.version}</version>
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</dependency>
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<dependency>
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<groupId>commons-beanutils</groupId>
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<artifactId>commons-beanutils</artifactId>
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<version>${commons-beanutils.version}</version>
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</dependency>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-jexl</artifactId>
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<version>${commons-jexl.version}</version>
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</dependency>
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<dependency>
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<groupId>org.tukaani</groupId>
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<artifactId>xz</artifactId>
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<apache-commons-text.version>1.10.0</apache-commons-text.version>
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<commons-net.version>3.6</commons-net.version>
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<mockftpserver.version>2.7.1</mockftpserver.version>
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<commons-configuration2.version>2.10.0</commons-configuration2.version>
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<commons-beanutils.version>1.9.4</commons-beanutils.version>
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<commons-jexl.version>2.1.1</commons-jexl.version>
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<xz.version>1.9</xz.version>
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<zstd-jni.version>1.5.5-11</zstd-jni.version>
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</properties>

‎libraries-apache-commons-2/src/main/java/com/baeldung/commons/configuration/CustomDecoder.java

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package com.baeldung.commons.configuration;
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import org.apache.commons.configuration2.ConfigurationDecoder;
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import org.apache.commons.net.util.Base64;
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public class CustomDecoder implements ConfigurationDecoder {
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@Override
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public String decode(String encodedValue) {
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return new String(Base64.decodeBase64(encodedValue));
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}
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}

‎libraries-apache-commons-2/src/main/java/com/baeldung/commons/configuration/ExternalServices.java

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package com.baeldung.commons.configuration;
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public class ExternalServices {
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public static final String BAELDUNG_WEBSITE = "https://www.baeldung.com";
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}

‎libraries-apache-commons-2/src/test/java/com/baeldung/commons/configuration/ConfigurationClassUnitTest.java

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package com.baeldung.commons.configuration;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNull;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.io.File;
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import java.util.List;
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import java.util.NoSuchElementException;
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import org.apache.commons.configuration2.AbstractConfiguration;
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import org.apache.commons.configuration2.Configuration;
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import org.apache.commons.configuration2.PropertiesConfiguration;
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import org.apache.commons.configuration2.XMLConfiguration;
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import org.apache.commons.configuration2.builder.fluent.Configurations;
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import org.apache.commons.configuration2.convert.DefaultListDelimiterHandler;
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import org.apache.commons.configuration2.ex.ConfigurationException;
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import org.apache.commons.configuration2.ex.ConversionException;
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import org.junit.jupiter.api.Test;
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class ConfigurationClassUnitTest {
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@Test
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void givenPropertiesFile_whenReadingWithConfigurationClass_thenIsLoaded() throws ConfigurationException {
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Configurations configs = new Configurations();
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Configuration config = configs.properties(new File("src/test/resources/configuration/file.properties"));
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String dbHost = config.getString("db.host");
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int dbPort = config.getInt("db.port");
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String dbUser = config.getString("db.user");
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String dbPassword = config.getString("undefinedKey", "defaultValue");
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assertEquals("baeldung.com", dbHost);
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assertEquals(9999, dbPort);
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assertEquals("admin", dbUser);
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assertEquals("defaultValue", dbPassword);
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}
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@Test
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void givenXMLFile_whenReadingWithConfigurationClass_thenIsLoaded() throws ConfigurationException {
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Configurations configs = new Configurations();
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XMLConfiguration config = configs.xml(new File("src/test/resources/configuration/hierarchical.xml"));
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String appender = config.getString("appender[@name]");
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List<String> encoderPatterns = config.getList(String.class, "appender.encoder.pattern");
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String pattern1 = config.getString("appender.encoder.pattern(0)");
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assertEquals("STDOUT", appender);
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assertEquals(2, encoderPatterns.size());
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assertEquals("Pattern1", pattern1);
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}
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@Test
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void givenPropertiesFile_whenCopyingConfiguration_thenIsSuccessful() throws ConfigurationException {
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Configurations configs = new Configurations();
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Configuration baseConfig = configs.properties(new File("src/test/resources/configuration/file.properties"));
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Configuration subConfig = new PropertiesConfiguration();
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subConfig.addProperty("db.host", "baeldung");
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subConfig.addProperty("db.driver", "dummyDriver");
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((AbstractConfiguration) subConfig).copy(baseConfig);
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String dbHost = subConfig.getString("db.host");
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String dbDriver = subConfig.getString("db.driver");
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int dbPort = subConfig.getInt("db.port");
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String dbUser = subConfig.getString("db.user");
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assertEquals("baeldung.com", dbHost);
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assertEquals(9999, dbPort);
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assertEquals("admin", dbUser);
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assertEquals("dummyDriver", dbDriver);
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}
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@Test
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public void givenPropertiesFile_whenAppendingConfiguration_thenIsSuccessful() throws ConfigurationException {
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Configurations configs = new Configurations();
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Configuration baseConfig = configs.properties(new File("src/test/resources/configuration/file.properties"));
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Configuration subConfig = new PropertiesConfiguration();
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subConfig.addProperty("db.host", "baeldung");
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subConfig.addProperty("db.driver", "dummyDriver");
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((AbstractConfiguration) subConfig).append(baseConfig);
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String dbHost = subConfig.getString("db.host");
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String dbDriver = subConfig.getString("db.driver");
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int dbPort = subConfig.getInt("db.port");
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String dbUser = subConfig.getString("db.user");
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assertEquals("baeldung", dbHost);
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assertEquals(9999, dbPort);
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assertEquals("admin", dbUser);
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assertEquals("dummyDriver", dbDriver);
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}
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@Test
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void givenXMLFile_whenCloningConfiguration_thenIsSuccessful() throws ConfigurationException {
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Configurations configs = new Configurations();
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XMLConfiguration baseConfig = configs.xml(new File("src/test/resources/configuration/hierarchical.xml"));
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XMLConfiguration subConfig = new XMLConfiguration();
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//subConfig = (XMLConfiguration) baseConfig.clone();
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subConfig = new XMLConfiguration(baseConfig);
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String appender = subConfig.getString("appender[@name]");
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List<String> encoderPatterns = subConfig.getList(String.class, "appender.encoder.pattern");
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String pattern1 = subConfig.getString("appender.encoder.pattern(0)");
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assertEquals("STDOUT", appender);
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assertEquals(2, encoderPatterns.size());
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assertEquals("Pattern1", pattern1);
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}
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@Test
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void givenEncodedProperty_whenCustomDecoderImplemented_thenIsSuccessful() throws ConfigurationException {
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Configurations configs = new Configurations();
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Configuration config = configs.properties(new File("src/test/resources/configuration/file.properties"));
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((AbstractConfiguration) config).setConfigurationDecoder(new CustomDecoder());
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assertEquals("mySecretString", config.getEncodedString("db.password"));
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}
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@Test
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void whenDataTypeConversionAttempted_thenIsSuccessful() {
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Configuration config = new PropertiesConfiguration();
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config.addProperty("stringProperty", "This is a string");
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config.addProperty("numericProperty", "9999");
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config.addProperty("booleanProperty", "true");
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assertEquals("This is a string", config.getString("stringProperty"));
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assertEquals(9999, config.getInt("numericProperty"));
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assertTrue(config.getBoolean("booleanProperty"));
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}
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@Test
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void whenDataTypeConversionAttempted_thenThrowsException() {
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Configuration config = new PropertiesConfiguration();
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config.addProperty("numericProperty", "9999a");
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assertThrows(ConversionException.class, () -> config.getInt("numericProperty"));
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}
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@Test
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void whenInterpolationIsAttempted_thenIsSuccessful() throws ConfigurationException {
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System.setProperty("user.name", "Baeldung");
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Configurations configs = new Configurations();
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Configuration config = configs.properties(new File("src/test/resources/configuration/file.properties"));
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String dbUrl = config.getString("db.url");
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String userName = config.getString("db.username");
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String externalService = config.getString("db.external-service");
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assertEquals("baeldung.com:9999", dbUrl);
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assertEquals("Baeldung", userName);
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assertEquals("https://www.baeldung.com", externalService);
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}
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@Test
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void whenDelimiterIsSpecified_thenMultiValuePropertyIsLoaded() {
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PropertiesConfiguration propertiesConfig = new PropertiesConfiguration();
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propertiesConfig.setListDelimiterHandler(new DefaultListDelimiterHandler(';'));
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propertiesConfig.addProperty("delimitedProperty", "admin;read-only;read-write");
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propertiesConfig.addProperty("arrayProperty", "value1;value2");
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List<Object> delimitedProperties = propertiesConfig.getList("delimitedProperty");
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String[] arrayProperties = propertiesConfig.getStringArray("arrayProperty");
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assertEquals(3, delimitedProperties.size());
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assertEquals("admin", delimitedProperties.get(0));
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assertEquals(2, arrayProperties.length);
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assertEquals("value1", propertiesConfig.getString("arrayProperty"));
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}
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@Test
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void whenPropertiesAreMissing_thenIsHandled() {
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PropertiesConfiguration propertiesConfig = new PropertiesConfiguration();
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String objectProperty = propertiesConfig.getString("anyProperty");
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int primitiveProperty = propertiesConfig.getInt("anyProperty", 1);
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assertNull(objectProperty);
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assertEquals(1, primitiveProperty);
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}
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@Test
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void whenPropertiesAreMissing_thenExceptionIsThrown() {
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PropertiesConfiguration propertiesConfig = new PropertiesConfiguration();
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assertThrows(NoSuchElementException.class, () -> propertiesConfig.getInt("anyProperty"));
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}
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}

‎libraries-apache-commons-2/src/test/java/com/baeldung/commons/configuration/FileBasedConfigurationBuilderUnitTest.java

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package com.baeldung.commons.configuration;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import org.apache.commons.configuration2.Configuration;
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import org.apache.commons.configuration2.FileBasedConfiguration;
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import org.apache.commons.configuration2.PropertiesConfiguration;
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import org.apache.commons.configuration2.XMLConfiguration;
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import org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder;
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import org.apache.commons.configuration2.builder.fluent.Parameters;
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import org.apache.commons.configuration2.ex.ConfigurationException;
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import org.apache.commons.configuration2.interpol.ConfigurationInterpolator;
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import org.apache.commons.configuration2.interpol.ExprLookup;
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import org.apache.commons.configuration2.interpol.Lookup;
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import org.junit.jupiter.api.Test;
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class FileBasedConfigurationBuilderUnitTest {
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@Test
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void whenReadingPropertiesFile_thenIsSuccessful() throws ConfigurationException {
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Parameters params = new Parameters();
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FileBasedConfigurationBuilder<FileBasedConfiguration> builder = new FileBasedConfigurationBuilder<FileBasedConfiguration>(
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PropertiesConfiguration.class).configure(params.properties()
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.setFileName("src/test/resources/configuration/file1.properties"));
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Configuration config = builder.getConfiguration();
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String dbHost = config.getString("db.host");
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int dbPort = config.getInt("db.port");
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String dbUser = config.getString("db.user");
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assertEquals("baeldung.com", dbHost);
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assertEquals(9999, dbPort);
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assertEquals("admin", dbUser);
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}
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@Test
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void whenReadingXMLFile_thenIsSuccessful() throws ConfigurationException {
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Parameters params = new Parameters();
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FileBasedConfigurationBuilder<XMLConfiguration> builder = new FileBasedConfigurationBuilder<>(XMLConfiguration.class).configure(params.xml()
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.setFileName("src/test/resources/configuration/hierarchical.xml")
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.setValidating(true));
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XMLConfiguration config = builder.getConfiguration();
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String appender = config.getString("appender[@name]");
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List<String> encoderPatterns = config.getList(String.class, "appender.encoder.pattern");
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assertEquals("STDOUT", appender);
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assertEquals(2, encoderPatterns.size());
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}
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@Test
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void whenExpressionEvaluationIsAttempted_thenIsSuccessful() throws ConfigurationException {
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System.setProperty("user.home", "/usr/lib");
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Parameters params = new Parameters();
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Map<String, Lookup> lookups = new HashMap<>(ConfigurationInterpolator.getDefaultPrefixLookups());
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ExprLookup.Variables variables = new ExprLookup.Variables();
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variables.add(new ExprLookup.Variable("System", "Class:java.lang.System"));
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ExprLookup exprLookup = new ExprLookup(variables);
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exprLookup.setInterpolator(new ConfigurationInterpolator());
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lookups.put("expr", exprLookup);
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FileBasedConfigurationBuilder<FileBasedConfiguration> builder = new FileBasedConfigurationBuilder<FileBasedConfiguration>(
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PropertiesConfiguration.class).configure(params.properties()
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.setFileName("src/test/resources/configuration/file1.properties")
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.setPrefixLookups(lookups));
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Configuration config = builder.getConfiguration();
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String dbDumpLocation = config.getString("db.data-dump-location");
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assertEquals("/usr/lib/dump.dat", dbDumpLocation);
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}
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}

‎libraries-apache-commons-2/src/test/java/com/baeldung/commons/configuration/MultiFileConfigurationBuilderUnitTest.java

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package com.baeldung.commons.configuration;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import org.apache.commons.configuration2.Configuration;
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import org.apache.commons.configuration2.PropertiesConfiguration;
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import org.apache.commons.configuration2.builder.combined.MultiFileConfigurationBuilder;
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import org.apache.commons.configuration2.builder.fluent.Parameters;
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import org.apache.commons.configuration2.ex.ConfigurationException;
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import org.apache.commons.configuration2.interpol.ConfigurationInterpolator;
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import org.junit.jupiter.api.Test;
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class MultiFileConfigurationBuilderUnitTest {
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@Test
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void givenMultiplePropertyFiles_whenReadingWithMultiFileConfigurationBuilder_thenIsLoaded() throws ConfigurationException {
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System.setProperty("tenant", "A");
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String filePattern = "src/test/resources/configuration/tenant-${sys:tenant}.properties";
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MultiFileConfigurationBuilder<PropertiesConfiguration> builder = new MultiFileConfigurationBuilder<>(PropertiesConfiguration.class).configure(
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new Parameters().multiFile()
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.setFilePattern(filePattern)
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.setPrefixLookups(ConfigurationInterpolator.getDefaultPrefixLookups()));
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Configuration config = builder.getConfiguration();
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String tenantAName = config.getString("name");
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assertEquals("Tenant A", tenantAName);
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}
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}

‎libraries-apache-commons-2/src/test/resources/configuration/file.properties

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db.host=baeldung.com
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db.port=9999
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db.user=admin
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db.password=bXlTZWNyZXRTdHJpbmc=
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db.url=${db.host}:${db.port}
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db.username=${sys:user.name}
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db.external-service=${const:com.baeldung.commons.configuration.ExternalServices.BAELDUNG_WEBSITE}
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db.data-dump-location=${expr:System.getProperty("user.home")}/dump.dat

‎libraries-apache-commons-2/src/test/resources/configuration/file1.properties

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db.host=baeldung.com
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include=file.properties
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includeOptional=file2.properties

‎libraries-apache-commons-2/src/test/resources/configuration/hierarchical.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE configuration SYSTEM "validation-sample.dtd">
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<configuration>
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<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
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<encoder>
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<pattern>Pattern1</pattern>
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<pattern>Pattern2</pattern>
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</encoder>
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</appender>
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<root>
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<appender-ref ref="STDOUT" />
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</root>
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</configuration>

‎libraries-apache-commons-2/src/test/resources/configuration/tenant-A.properties

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name=Tenant A

‎libraries-apache-commons-2/src/test/resources/configuration/validation-sample.dtd

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<!ELEMENT configuration (appender+, root)>
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<!ELEMENT appender (encoder?)>
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<!ATTLIST appender
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name CDATA #REQUIRED
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class CDATA #REQUIRED
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>
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<!ELEMENT encoder (pattern+)>
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<!ELEMENT pattern (#PCDATA)>
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<!ELEMENT root (appender-ref+)>
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<!ELEMENT appender-ref EMPTY>
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<!ATTLIST appender-ref
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ref CDATA #REQUIRED
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>

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