[BAEL-7669] Example code for article. Setting global TimeZone in spring (#16260)

* [BAEL-7669] Example code for article. Setting global TimeZone in spring

* Added logback-test.xml for spring tests, to set level to INFO

* [BAEL-7669] Switched to spring-boot-application to include more examples

* Added things needed in pom.xml, without affecting existing versions

* [BAEL-7669] After code review: exported spring boot version in property

- Fixed constant name, to follow the uppercase convention
- Added comments to explain the commented out options, as described in the article

* [BAEL-7669] Added example of reading timezone value from properties file

* [BAEL-7669] Moved code to spring-boot-customization module

spring-boot-modules/spring-boot-basic-customization-3/src/main/java/com/baeldung/globaltimezone/GlobalTimeZoneBean.java

@@ -0,0 +1,28 @@
+package com.baeldung.globaltimezone;
+
+import java.util.TimeZone;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+
+@Component
+public class GlobalTimeZoneBean {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(GlobalTimeZoneBean.class);
+
+    private final String globalTimeZone;
+
+    public GlobalTimeZoneBean() {
+        // TimeZone.setDefault(TimeZone.getTimeZone("GMT+08:00"));
+        LOGGER.info("Default timezone, during beans creation, is set to: " + TimeZone.getDefault()
+            .getDisplayName());
+
+        globalTimeZone = TimeZone.getDefault()
+            .getDisplayName();
+    }
+
+    public String getGlobalTimeZone() {
+        return globalTimeZone;
+    }
+}

spring-boot-modules/spring-boot-basic-customization-3/src/main/java/com/baeldung/globaltimezone/GlobalTimezoneBeanFactoryPostProcessor.java

@@ -0,0 +1,24 @@
+package com.baeldung.globaltimezone;
+
+import java.util.TimeZone;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.stereotype.Component;
+
+@Component
+public class GlobalTimezoneBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(GlobalTimezoneBeanFactoryPostProcessor.class);
+
+    @Override
+    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+        LOGGER.info("Default timezone, before bean factory post processor, is set to: " + TimeZone.getDefault()
+            .getDisplayName());
+
+        TimeZone.setDefault(TimeZone.getTimeZone("GMT+08:00"));
+    }
+}

spring-boot-modules/spring-boot-basic-customization-3/src/main/java/com/baeldung/globaltimezone/MainApplication.java

@@ -0,0 +1,37 @@
+package com.baeldung.globaltimezone;
+
+import java.util.TimeZone;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+import jakarta.annotation.PostConstruct;
+
+@SpringBootApplication
+public class MainApplication {
+
+    @Value("${application.timezone:UTC}")
+    private String applicationTimeZone;
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(MainApplication.class);
+
+    public static void main(String[] args) {
+        // For having the value available from the very early stages of the execution, even before detecting the Spring Profile, set the value here:
+        // TimeZone.setDefault(TimeZone.getTimeZone("GMT+08:00"));
+        LOGGER.info("Default timezone, before main run, is set to: " + TimeZone.getDefault()
+            .getDisplayName());
+
+        SpringApplication.run(MainApplication.class, args);
+    }
+
+    @PostConstruct
+    public void executeAfterMain() {
+        // For having the value available just after WebApplicationContext initialization  is completed and using application properties:
+        // TimeZone.setDefault(TimeZone.getTimeZone(applicationTimeZone));
+        LOGGER.info("Default timezone, after main run, is set to: " + TimeZone.getDefault()
+            .getDisplayName());
+    }
+}

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

@@ -0,0 +1 @@
+application.timezone=GMT+08:00

spring-boot-modules/spring-boot-basic-customization-3/src/test/java/com/baeldung/globaltimezone/GlobalTimezoneBeanFactoryPostProcessorUnitTest.java

@@ -0,0 +1,19 @@
+package com.baeldung.globaltimezone;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest(classes = MainApplication.class)
+class GlobalTimezoneBeanFactoryPostProcessorUnitTest {
+
+    @Autowired
+    private GlobalTimeZoneBean globalTimeZoneBean;
+
+    @Test
+    void givenUTCTimeZoneSetInBeanFactoryPostProcessor_whenRetrieveGlobalTimeZone_thenReturnUTC() {
+        assertThat(globalTimeZoneBean.getGlobalTimeZone()).isEqualTo("GMT+08:00");
+    }
+}

spring-boot-modules/spring-boot-basic-customization-3/src/test/resources/logback-test.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration scan="true" scanPeriod="15 seconds" debug="false">
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>[%d{ISO8601}]-[%thread] %-5level %logger - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>