BAEL-923 How to inject a value from properties to a class not managed by Spring? (#1878)

* adam.zawada@gmail.com - Different Types of Bean Injection in Spring

* adam.zawada@gmail.com - Different Types of Bean Injection in Spring
switch to Java based configuration

* BAEL-895 calculate the period/duration between two dates in Java 8

* clean old PR

* BAEL-923 How to inject a value from properties to a class not managed by Spring?

* clean PR

core-java/src/main/java/com/baeldung/util/PropertiesLoader.java

@@ -0,0 +1,19 @@
+package com.baeldung.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Properties;
+
+public class PropertiesLoader {
+
+    public static Properties loadProperties(String resourceFileName) throws IOException {
+        Properties configuration = new Properties();
+        InputStream inputStream = PropertiesLoader.class
+          .getClassLoader()
+          .getResourceAsStream(resourceFileName);
+        configuration.load(inputStream);
+        inputStream.close();
+        return configuration;
+    }
+
+}

core-java/src/test/java/com/baeldung/util/PropertiesLoaderTest.java

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+package com.baeldung.util;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Properties;
+
+import static org.junit.Assert.assertEquals;
+
+public class PropertiesLoaderTest {
+
+    @Test
+    public void loadProperties_whenPropertyReaded_thenSuccess() throws IOException {
+        //given
+        final String RESOURCE_FILE_NAME = "configuration.properties";
+
+        final String SAMPLE_CONF_ENTRY = "sampleConfEntry";
+        final String COLON_SEPARATED_CONF_ENTRY = "colonSeparatedEntry";
+
+        final String GIVEN_CONF_ENTRY_VALUE = "sample String value";
+        final String COLON_SEPARATED_CONF_ENTRY_VALUE = "colon separated entry value";
+
+        //when
+        Properties config = PropertiesLoader.loadProperties(RESOURCE_FILE_NAME);
+
+        String sampleConfEntryValue = config.getProperty(SAMPLE_CONF_ENTRY);
+        String colonSeparatedConfEntryValue = config.getProperty(COLON_SEPARATED_CONF_ENTRY);
+
+        //then
+        assertEquals(GIVEN_CONF_ENTRY_VALUE, sampleConfEntryValue);
+        assertEquals(COLON_SEPARATED_CONF_ENTRY_VALUE, colonSeparatedConfEntryValue);
+
+    }
+}

core-java/src/test/resources/configuration.properties

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+# this is sample property file for PropertiesLoaderTest configuration needs
+! this is also a comment
+sampleConfEntry = sample String value
+colonSeparatedEntry : colon separated entry value