[BAEL-9643] - Create code for Properties article

core-java/src/test/java/com/baeldung/java/properties/PropertiesUnitTest.java

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+package com.baeldung.java.properties;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.Properties;
+
+import org.junit.Test;
+
+public class PropertiesUnitTest {
+
+    @Test
+    public void givenPropertyValue_whenPropertiesFileLoaded_thenCorrect() throws IOException {
+     
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        String catalogConfigPath = rootPath + "catalog";
+        
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+         
+        Properties catalogProps = new Properties();
+        catalogProps.load(new FileInputStream(catalogConfigPath));
+        
+        String appVersion = appProps.getProperty("version");
+        assertEquals("1.0", appVersion);
+        
+        assertEquals("files", catalogProps.getProperty("c1"));
+    }
+    
+    @Test
+    public void givenPropertyValue_whenXMLPropertiesFileLoaded_thenCorrect() throws IOException {
+     
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String iconConfigPath = rootPath + "icons.xml";
+        Properties iconProps = new Properties();
+        iconProps.loadFromXML(new FileInputStream(iconConfigPath));
+        
+        assertEquals("icon1.jpg", iconProps.getProperty("fileIcon"));
+    }
+    
+    @Test
+    public void givenAbsentProperty_whenPropertiesFileLoaded_thenReturnsDefault() throws IOException {
+    
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+        
+        String appVersion = appProps.getProperty("version");
+        String appName = appProps.getProperty("name", "defaultName");
+        String appGroup = appProps.getProperty("group", "baeldung");
+        String appDownloadAddr = appProps.getProperty("downloadAddr");
+        
+        assertEquals("1.0", appVersion);
+        assertEquals("TestApp", appName);
+        assertEquals("baeldung", appGroup);
+        assertNull(appDownloadAddr);
+    }
+    
+    @Test(expected = Exception.class)
+    public void givenImproperObjectCasting_whenPropertiesFileLoaded_thenThrowsException() throws IOException {
+        
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+        
+        float appVerFloat = (float) appProps.get("version");
+    }
+    
+    @Test
+    public void givenPropertyValue_whenPropertiesSet_thenCorrect() throws IOException {
+        
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+        
+        appProps.setProperty("name", "NewAppName");
+        appProps.setProperty("downloadAddr", "www.baeldung.com/downloads");
+        
+        String newAppName = appProps.getProperty("name");
+        assertEquals("NewAppName", newAppName);
+        
+        String newAppDownloadAddr = appProps.getProperty("downloadAddr");
+        assertEquals("www.baeldung.com/downloads", newAppDownloadAddr);
+    }
+    
+    @Test
+    public void givenPropertyValueNull_whenPropertiesRemoved_thenCorrect() throws IOException {
+        
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+        
+        String versionBeforeRemoval = appProps.getProperty("version");
+        assertEquals("1.0", versionBeforeRemoval);
+
+        appProps.remove("version");    
+        String versionAfterRemoval = appProps.getProperty("version");
+        assertNull(versionAfterRemoval);
+    }
+    
+    @Test
+    public void whenPropertiesStoredInFile_thenCorrect() throws IOException {
+        
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties();
+        appProps.load(new FileInputStream(appConfigPath));
+        
+        String newAppConfigPropertiesFile = rootPath + "newApp.properties";
+        appProps.store(new FileWriter(newAppConfigPropertiesFile), "store to properties file");
+        
+        String newAppConfigXmlFile = rootPath + "newApp.xml";
+        appProps.storeToXML(new FileOutputStream(newAppConfigXmlFile), "store to xml file");
+    }
+    
+    @Test
+    public void givenPropertyValueAbsent_LoadsValuesFromDefaultProperties() throws IOException {
+        
+        String rootPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
+        
+        String defaultConfigPath = rootPath + "default.properties";
+        Properties defaultProps = new Properties();
+        defaultProps.load(new FileInputStream(defaultConfigPath));
+         
+        String appConfigPath = rootPath + "app.properties";
+        Properties appProps = new Properties(defaultProps);
+        appProps.load(new FileInputStream(appConfigPath));
+         
+        String appName = appProps.getProperty("name");        
+        String appVersion = appProps.getProperty("version");
+        String defaultSite = appProps.getProperty("site");
+        
+        assertEquals("1.0", appVersion);
+        assertEquals("TestApp", appName);
+        assertEquals("www.google.com", defaultSite);
+    }
+}

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

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+version=1.0
+name=TestApp
+date=2016-11-12

core-java/src/test/resources/catalog

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+c1=files
+c2=images
+c3=videos

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

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+site=www.google.com
+name=DefaultAppName
+topic=Properties
+category=core-java

core-java/src/test/resources/icons.xml

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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
+<properties>
+    <comment>xml example</comment>
+    <entry key="fileIcon">icon1.jpg</entry>
+    <entry key="imageIcon">icon2.jpg</entry>
+    <entry key="videoIcon">icon3.jpg</entry>
+</properties>