{"id":328961,"date":"2023-10-02T20:39:39","date_gmt":"2023-10-02T20:39:39","guid":{"rendered":"https:\/\/www.baeldung.com\/java-detect-the-username"},"modified":"2023-10-02T20:39:39","modified_gmt":"2023-10-02T20:39:39","slug":"how-to-detect-the-username-using-java","status":"publish","type":"post","link":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/2023\/10\/02\/how-to-detect-the-username-using-java\/","title":{"rendered":"How to Detect the Username Using Java"},"content":{"rendered":"

<\/p>\n

\"\"<\/p>\n

1. Overview<\/h2>\n
<\/div>\n

Sometimes, working with Java applications, we need to access the values of system properties and environment variables.<\/p>\n

In this tutorial, we’ll learn how to retrieve the user name from a running Java application.<\/p>\n

2. System.getProperty<\/em><\/h2>\n
<\/div>\n

One way to get information about the user, more precisely, its name, we can use the System.getProperty(String).\u00a0<\/em>This method takes the key. Usually, they’re uniform and predefined<\/a>, such as java.version<\/em>, os.name<\/em><\/a>, user.home<\/em>, etc.<\/strong> In our case, we’re interested in the user.name<\/em>:<\/p>\n

String username = System.getProperty("user.name");\r\nSystem.out.println("User: " + username);<\/code><\/pre>\n
An overloaded version of this method System can protect us from non-existent properties.getProperty(String, String), <\/em>which takes a default value.<\/p>\n
String customProperty = System.getProperty("non-existent-property", "default value");\r\nSystem.out.println("Custom property: " + customProperty);<\/code><\/pre>\n
Aside from working with predefined system properties, this method allows us to get the values of the custom properties we’ve passed with the -D<\/em> prefix<\/a>. If we run our application with the following command:<\/p>\n
java -jar app.jar -Dcustom.prop=`Hello World!`<\/code><\/pre>\n
Inside an application, we can use this value<\/p>\n
String customProperty = System.getProperty("custom.prop");\r\nSystem.out.println("Custom property: " + customProperty);<\/code><\/pre>\n
This can help us make flexible and extensible codebase by passing values at the startup.<\/p>\n
Additionally, it’s possible to use\u00a0System.setProperty<\/em>, but changing crucial properties might have unpredictable effects on the system.<\/p>\n
3. System.getenv<\/em><\/h2>\n
<\/div>\n
Additionally, we can use environment variables<\/a> to get a user name.<\/strong> Usually, it can be found by either\u00a0USERNAME<\/em> or\u00a0USER:<\/em><\/p>\n
String username = System.getenv("USERNAME");\r\nSystem.out.println("User: " + username);<\/code><\/pre>\n
The environment variables are read-only but also provide an excellent mechanism to get information about the system the application runs in.<\/p>\n
4. Conclusion<\/h2>\n
<\/div>\n
In this article, we discussed a couple of ways to get the required information about the environment. Environment variables and properties are a convenient way to gain more information about the system. Also, they allow custom variables to make an application more flexible.<\/p>\n
As usual, all the examples are available over on GitHub<\/a>.<\/p>\n
\"\"<\/p>\n
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<\/p>","protected":false},"excerpt":{"rendered":"
\"\"<\/p>\n
Explore a couple of ways to get the required information about the environment.<\/p>\n
<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/div>\n<\/div>","protected":false},"author":2004,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"How to Detect the Username Using Java - ITTeacherITFreelance.hk","description":"Explore a couple of ways to get the required information about the environment. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0"},"footnotes":""},"categories":[6,1307],"tags":[],"_links":{"self":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328961"}],"collection":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/2004"}],"replies":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=328961"}],"version-history":[{"count":1,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328961\/revisions"}],"predecessor-version":[{"id":328962,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328961\/revisions\/328962"}],"wp:attachment":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=328961"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/categories?post=328961"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/tags?post=328961"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}