BAEL-748 quick guide to @Value (#1577)

* BAEL-748 quick guide to @Value

* BAEL-748 changes from review

spring-core/src/main/java/com/baeldung/value/SomeBean.java

@@ -0,0 +1,17 @@
+package com.baeldung.value;
+
+public class SomeBean {
+    private int someValue;
+
+    public SomeBean(int someValue) {
+        this.someValue = someValue;
+    }
+
+    public int getSomeValue() {
+        return someValue;
+    }
+
+    public void setSomeValue(int someValue) {
+        this.someValue = someValue;
+    }
+}

spring-core/src/main/java/com/baeldung/value/ValuesApp.java

@@ -0,0 +1,68 @@
+package com.baeldung.value;
+
+import java.util.List;
+
+import javax.annotation.PostConstruct;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.PropertySource;
+
+@Configuration
+@PropertySource(name = "myProperties", value = "values.properties")
+public class ValuesApp {
+
+    @Value("string value")
+    private String stringValue;
+
+    @Value("${value.from.file}")
+    private String valueFromFile;
+
+    @Value("${systemValue}")
+    private String systemValue;
+
+    @Value("${unknown_param:some default}")
+    private String someDefault;
+
+    @Value("${priority}")
+    private String prioritySystemProperty;
+
+    @Value("#{systemProperties['priority']}")
+    private String spelValue;
+
+    @Value("#{systemProperties['unknown'] ?: 'some default'}")
+    private String spelSomeDefault;
+
+    @Value("#{someBean.someValue}")
+    private Integer someBeanValue;
+
+    @Value("#{'${listOfValues}'.split(',')}")
+    private List<String> valuesList;
+
+    public static void main(String[] args) {
+        System.setProperty("systemValue", "Some system parameter value");
+        System.setProperty("priority", "System property");
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ValuesApp.class);
+    }
+
+    @Bean
+    public SomeBean someBean() {
+        return new SomeBean(10);
+    }
+
+    @PostConstruct
+    public void afterInitialize() {
+        System.out.println(stringValue);
+        System.out.println(valueFromFile);
+        System.out.println(systemValue);
+        System.out.println(someDefault);
+        System.out.println(prioritySystemProperty);
+        System.out.println(spelValue);
+        System.out.println(spelSomeDefault);
+        System.out.println(someBeanValue);
+        System.out.println(valuesList);
+    }
+}

spring-core/src/main/resources/values.properties

@@ -0,0 +1,3 @@
+value.from.file=Value got from the file
+priority=Properties file
+listOfValues=A,B,C