Move articles from spring-core-6 module to other spring-boot modules (#13722)

* Move articles from spring-core-6 module to other spring-boot modules

* JAVA-19559 Move articles from spring-core-6 module to other spring-boot-3 modules

* JAVA-19559 Minor spacing change

* JAVA-19559 Revert  Minor spacing change

spring-boot-modules/spring-boot-properties-3/src/main/java/com/baeldung/envvariables/BaeldungProperties.java

@@ -0,0 +1,20 @@
+package com.baeldung.envvariables;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.stereotype.Component;
+
+@Component
+@ConfigurationProperties(prefix = "baeldung")
+public class BaeldungProperties {
+
+    private String presentation;
+
+    public String getPresentation() {
+        return presentation;
+    }
+
+    public void setPresentation(String presentation) {
+        this.presentation = presentation;
+    }
+
+}

spring-boot-modules/spring-boot-properties-3/src/main/java/com/baeldung/envvariables/MyController.java

@@ -0,0 +1,60 @@
+package com.baeldung.envvariables;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.core.env.Environment;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class MyController {
+
+    @Value("${environment.name}")
+    private String environmentName;
+
+    @Value("${java.home.and.environment}")
+    private String javaHomeAndEnvironmentName;
+
+    @Value("${thispropertydoesnotexist}")
+    private String nonExistentProperty;
+
+    @Value("${baeldung.presentation}")
+    private String baeldungPresentation;
+
+    @Autowired
+    private Environment environment;
+
+    @Autowired
+    private BaeldungProperties baeldungProperties;
+
+    @GetMapping("/environment_name")
+    String getEnvironmentName_FromEnvironmentVariables() {
+        return environmentName;
+    }
+
+    @GetMapping("/java_home_and_environment")
+    String getJavaHomeAndEnvironmentName_FromEnvironmentVariables() {
+        return javaHomeAndEnvironmentName;
+    }
+
+    @GetMapping("non_existent_property")
+    String getNonexistentProperty_FromEnvironmentVariables() {
+        return nonExistentProperty;
+    }
+
+    @GetMapping("baeldung_presentation_from_value")
+    String getBaeldungPresentation_FromValue() {
+        return baeldungPresentation;
+    }
+
+    @GetMapping("baeldung_presentation_from_environment")
+    String getBaeldungPresentation_FromEnvironment() {
+        return environment.getProperty("baeldung.presentation");
+    }
+
+    @GetMapping("baeldung_configuration_properties")
+    String getBaeldungPresentation_FromConfigurationProperties() {
+        return baeldungProperties.getPresentation();
+    }
+
+}

spring-boot-modules/spring-boot-properties-3/src/main/resources/application.properties

@@ -26,4 +26,9 @@ spring.config.activate.on-profile=multidocument-prod
 spring.datasource.password=password
 spring.datasource.url=jdbc:h2:prod
 spring.datasource.username=prodUser
-bael.property=prodValue
+bael.property=prodValue
+#---
+environment.name=${OS}
+java.home.and.environment=${JAVA_HOME}+${OS}
+not.existing.system.property=${thispropertydoesnotexist}
+baeldung.presentation=${HELLO_BAELDUNG}. Java is installed in the folder: ${JAVA_HOME}

spring-boot-modules/spring-boot-properties-3/src/test/java/com/baeldung/envvariables/MyControllerIntegrationTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.envvariables;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest(classes = MyController.class)
+@AutoConfigureMockMvc
+public class MyControllerIntegrationTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    /** NB : these tests are commented out because they are environment dependent
+     * If you want to run one of them on your machine, follow the instruction above it
+     *
+     * expects the value of your system environment property 'OS' (it is already defined at least in Windows_NT)
+     @Test void givenExistingSystemProperty_whenInjected_thenHasSystemPropertyValue() throws Exception {
+     mockMvc.perform(get("/environment_name"))
+     .andExpect(content().string(equalTo("Windows_NT")));
+     }
+    
+      * expects the value of the JAVA_HOME environment variable (you need to define it if you haven't yet), with a + and the 'OS' environment property in the end
+     @Test void givenCombinationOfSystemPropertyAndEnvironmentVariable_whenInjected_thenHasExpectedValue() throws Exception {
+     mockMvc.perform(get("/java_home_and_environment"))
+     .andExpect(content().string(equalTo("C:\\Program Files\\Java\\jdk-11.0.14+Windows_NT")));
+     }
+    
+      * expects the content to be ${thispropertydoesnotexist} ; if you have defined an environment property called thispropertydoesnotexist, it would fail
+     @Test void givenNonExistentProperty_whenInjected_thenKeepsTheStringValue() throws Exception {
+     mockMvc.perform(get("/non_existent_property"))
+     .andExpect(content().string(equalTo("${thispropertydoesnotexist}")));
+     }
+     */
+}