You may already be familiar with @Value annotation from Spring. This annotation allows you to inject some properties into your beans.<\/p>\n\n\n\n
But there\u2019s a lot of ways you could do that. And maybe you are not familiar with all of them.<\/p>\n\n\n\n
This article will show you many ways to work with @Value and some new ways you can apply to your projects.<\/p>\n\n\n\n
Let\u2019s explore our options!<\/p>\n\n\n\n
This is the most used option in Spring projects. It\u2019s the common way you can control feature flags, API keys, database connection details, etc.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("${feature.enableDarkMode}")\nprivate boolean isDarkModeEnabled;\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nfeature.enableDarkMode=true\n\n<\/pre><\/div>\n\n\n2. Hardcoded Values:<\/h3>\n\n\n\n
This way set the value as a constant in your code, this way you cannot change it externally.<\/p>\n\n\n
\n@Value("localhost")\nprivate String defaultServerAddress;\n\n<\/pre><\/div>\n\n\n3. Constructor Injection<\/h3>\n\n\n\n
Here is to create immutable beans that need their dependencies and values upfront.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\npublic TestBean(@Value("${mail.smtp.server}") String smtpServer) {\n this.smtpServer = smtpServer;\n}\n\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nmail.smtp.server=smtp.example.com\n\n<\/pre><\/div>\n\n\n4. SetUp Default Values:<\/h3>\n\n\n\n
You can provide default values when injecting your properties to avoid application crashes. If you do not have the property set, it will automatically pick the default value.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("${app.cache.ttl:60}") \/\/ Default TTL of 60 seconds if not configured\nprivate int cacheTimeToLive;\n\n<\/pre><\/div>\n\n\n5. Inject Using Set Method (Less common)<\/h3>\n\n\n\n
This is an option in some legacy code bases, where construction is not possible, this way of injection becomes an option.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("${log.level}")\npublic void setLogLevel(String logLevel) {\n this.logLevel = logLevel;\n}\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nlog.level=INFO\n\n<\/pre><\/div>\n\n\n6. Injecting an Array of values:<\/h3>\n\n\n\n
You can set an array of values, using comma-separated values, Spring will automatically split values and put them in the array positions. You can use this to set an array of allowed origins configured by properties.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("${cors.allowedOrigins}")\nprivate String[] allowedOrigins;\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\ncors.allowedOrigins=https:\/\/example1.com,<https:\/\/example2.com>\n\n<\/pre><\/div>\n\n\n7. Injecting a List of Values:<\/h3>\n\n\n\n
If you want more flexibility in your Java code, injecting a collection of values you can use SpEL to split values to create the list.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{'${notification.channels}'.split(',')}")\nprivate List<String> notificationChannels;\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nnotification.channels=EMAIL,SMS,PUSH\n\n<\/pre><\/div>\n\n\n8. Inject Maps<\/h3>\n\n\n\n
You can inject in a Java map a group of configurations that uses key-value pattern.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{${http.client.config}}")\nprivate Map<String, Integer> httpClientConfig;\n\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nhttp.client.config={timeout: 500, maxConnections: 100}\n\n<\/pre><\/div>\n\n\n9. Inject a Single Value From a Map<\/h3>\n\n\n\n
In the same way, you can inject an entire map of values, you can use SpEL to inject a single value using its key.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{${http.client.config}['timeout']}")\nprivate int timeout;\n\n<\/pre><\/div>\n\n\nProperties:<\/p>\n\n\n
\nhttp.client.config={timeout: 500, maxConnections: 100}\n\n<\/pre><\/div>\n\n\n10. Access System Properties<\/h3>\n\n\n\n
This method will allow you to get the system properties from the Java properties, also it gets all the properties that you set when running the application with the -D parameter.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{systemProperties['java.home']}")\nprivate String javaHome;\n\n<\/pre><\/div>\n\n\nIn this example, the java.home<\/code> is already passed automatically to the process. But if you want to access some custom property you can do this:<\/p>\n\n\n\n@Value("#{systemProperties['custom.property']}")\nprivate String javaHome;\n\n<\/pre><\/div>\n\n\nRunning the project with custom property:<\/p>\n\n\n
\njava -Dcustom.property="value" -jar app.jar\n\n<\/pre><\/div>\n\n\n11. Get Environment Variables:<\/h3>\n\n\n\n
You can read an environment variable from your system (if the application has access to the variable).<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{environment['MY_ENV_VAR']}")\nprivate String myEnvVar;\n\n<\/pre><\/div>\n\n\n12. Use SpEL and Create Dynamic Properties<\/h3>\n\n\n\n
One common problem developers have is that the team members can be working on different OS, so you can create a dynamic property based on the system to make things more flexible.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\n@Value("#{systemProperties['os.name'].toLowerCase().contains('windows') ? 'C:\\\\\\\\' : '\/'}")\nprivate String rootDirectory;\n\n<\/pre><\/div>\n\n\nThis will get the os.name<\/a> from the system and decide what is the root directory to inject the value.<\/p>\n\n\n\nThat\u2019s it! Now you have a whole set of new ways to configure your Spring applications with @Value!<\/p>\n\n\n\n
That will give you more flexibility and options. It will offer a solution that fills your needs. By understanding how it works you can write more maintainable Spring applications.<\/p>\n\n\n\n
Test out new ways of Injecting properties into your project!<\/p>\n\n\n\n
If you like this topic, make sure to follow me, in the following days, I\u2019ll be explaining more about the Spring annotations!<\/p>\n\n\n\n
Stay tuned!<\/p>\n\n\n\n
Willian Moya (@WillianFMoya) \/ X (twitter.com)<\/a><\/p>\n\n\n\nWillian Ferreira Moya | LinkedIn<\/a><\/p>\n\n\n\nReferences<\/h3>\n\n\n\n\n- Baeldung: Spring @Value Annotation<\/a><\/li>\n\n\n\n
- Spring Framework Documentation: @Value Annotations<\/a><\/li>\n\n\n\n
- DigitalOcean: Spring @Value Annotation<\/a><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
You may already be familiar with @Value annotation from Spring. This annotation allows you to inject some properties into your beans. But there\u2019s a lot of ways you could do that. And maybe you are not familiar with all of them. This article will show you many ways to work with @Value and some new […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[6],"tags":[13,18,20,22,23,26],"class_list":["post-195","post","type-post","status-publish","format-standard","hentry","category-spring","tag-java","tag-programming","tag-software-development","tag-spring-boot","tag-spring-framework","tag-technology"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=\/wp\/v2\/posts\/195","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=195"}],"version-history":[{"count":0,"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=\/wp\/v2\/posts\/195\/revisions"}],"wp:attachment":[{"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=195"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=195"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/springmasteryhub.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=195"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}