Properties with Spring and Spring Boot – 使用Spring和Spring Boot的属性

最后修改: 2013年 10月 15日


1. Overview


This tutorial will show how to set up and use properties in Spring via Java configuration and @PropertySource.


We’ll also see how properties work in Spring Boot.

我们还将看到属性在Spring Boot中如何工作。

2. Register a Properties File via Annotations


Spring 3.1 also introduces the new @PropertySource annotation as a convenient mechanism for adding property sources to the environment.

Spring 3.1还引入了新的@PropertySource注解作为向环境添加属性源的便捷机制。

We can use this annotation in conjunction with the @Configuration annotation:


public class PropertiesWithJavaConfig {

Another very useful way to register a new properties file is using a placeholder, which allows us to dynamically select the right file at runtime:



2.1. Defining Multiple Property Locations


The @PropertySource annotation is repeatable according to Java 8 conventions. Therefore, if we’re using Java 8 or higher, we can use this annotation to define multiple property locations:

@PropertySource 注解是可重复的根据Java 8惯例。因此,如果我们使用Java 8或更高版本,我们可以使用这个注解来定义多个属性位置。

public class PropertiesWithJavaConfig {

Of course, we can also use the @PropertySources annotation and specify an array of @PropertySource. This works in any supported Java version, not just in Java 8 or higher:

当然,我们也可以使用@PropertySources注解,并指定一个@PropertySource数组。这在任何支持的Java版本中都适用,而不仅仅是在Java 8或更高版本中。

public class PropertiesWithJavaConfig {

In either case, it’s worth noting that in the event of a property name collision, the last source read takes precedence.


3. Using/Injecting Properties


Injecting a property with the @Value annotation is straightforward:


@Value( "${jdbc.url}" )
private String jdbcUrl;

We can also specify a default value for the property:


@Value( "${jdbc.url:aDefaultUrl}" )
private String jdbcUrl;

The new PropertySourcesPlaceholderConfigurer added in Spring 3.1 resolve ${…} placeholders within bean definition property values and @Value annotations.

Spring 3.1中新增的PropertySourcesPlaceholderConfigurer 在Bean定义的属性值和@Value注释中解决${…}占位符

Finally, we can obtain the value of a property using the Environment API:

最后,我们可以使用Environment API获得一个属性的值。

private Environment env;

4. Properties With Spring Boot

4.使用Spring Boot的属性

Before we go into more advanced configuration options for properties, let’s spend some time looking at the new properties support in Spring Boot.

在我们进入更高级的属性配置选项之前,让我们花些时间看看Spring Boot中新的属性支持。

Generally speaking, this new support involves less configuration compared to standard Spring, which is of course one of the main goals of Boot.


4.1. the Default Property File默认属性文件

Boot applies its typical convention over configuration approach to property files. This means that we can simply put an file in our src/main/resources directory, and it will be auto-detected. We can then inject any loaded properties from it as normal.


So, by using this default file, we don’t have to explicitly register a PropertySource or even provide a path to a property file.


We can also configure a different file at runtime if we need to, using an environment property:


java -jar app.jar --spring.config.location=classpath:/

As of Spring Boot 2.3, we can also specify wildcard locations for configuration files.

Spring Boot 2.3开始,我们还可以为配置文件指定通配符位置

For example, we can set the spring.config.location property to config/*/:


java -jar app.jar --spring.config.location=config/*/

This way, Spring Boot will look for configuration files matching the config/*/ directory pattern outside of our jar file. This comes in handy when we have multiple sources of configuration properties.

这样,Spring Boot将在我们的jar文件之外寻找与config/*/目录模式相匹配的配置文件。当我们有多个配置属性的来源时,这就很方便了。

Since version 2.4.0, Spring Boot supports using multi-document properties files, similarly as YAML does by design:

2.4.0版本起,Spring Boot支持使用多文档属性文件,类似于YAML的设计


Note that for properties files, the three-dashes notation is preceded by a comment character (#).


4.2. Environment-Specific Properties File


If we need to target different environments, there’s a built-in mechanism for that in Boot.


We can simply define an file in the src/main/resources directory, and then set a Spring profile with the same environment name.


For example, if we define a “staging” environment, that means we’ll have to define a staging profile and then

例如,如果我们定义一个 “staging “环境,这意味着我们必须定义一个staging配置文件,然后

This env file will be loaded and will take precedence over the default property file. Note that the default file will still be loaded, it’s just that when there is a property collision, the environment-specific property file takes precedence.


4.3. Test-Specific Properties File


We might also have a requirement to use different property values when our application is under test.


Spring Boot handles this for us by looking in our src/test/resources directory during a test run. Again, default properties will still be injectable as normal but will be overridden by these if there is a collision.

Spring Boot通过在测试运行期间查看src/test/resources目录来为我们处理这个问题。同样,默认的属性仍然可以正常注入,但如果发生碰撞,将被这些属性所覆盖。

4.4. The @TestPropertySource Annotation

4.4.@TestPropertySource 注释

If we need more granular control over test properties, then we can use the @TestPropertySource annotation.


This allows us to set test properties for a specific test context, taking precedence over the default property sources:


public class FilePropertyInjectionUnitTest {

    private String foo;

    public void whenFilePropertyProvided_thenProperlyInjected() {

If we don’t want to use a file, we can specify names and values directly:


@TestPropertySource(properties = {"foo=bar"})
public class PropertyInjectionUnitTest {

    private String foo;

    public void whenPropertyProvided_thenProperlyInjected() {

We can also achieve a similar effect using the properties argument of the @SpringBootTest annotation:

我们也可以使用properties 参数来实现类似的效果,@SpringBootTest注解:

  properties = {"foo=bar"}, classes = SpringBootPropertiesTestApplication.class)
public class SpringBootPropertyInjectionIntegrationTest {

    private String foo;

    public void whenSpringBootPropertyProvided_thenProperlyInjected() {

4.5. Hierarchical Properties


If we have properties that are grouped together, we can make use of the @ConfigurationProperties annotation, which will map these property hierarchies into Java objects graphs.


Let’s take some properties used to configure a database connection:



And then let’s use the annotation to map them to a database object:


@ConfigurationProperties(prefix = "database")
public class Database {
    String url;
    String username;
    String password;

    // standard getters and setters

Spring Boot applies it’s convention over configuration approach again, automatically mapping between property names and their corresponding fields. All that we need to supply is the property prefix.

Spring Boot再次应用其约定俗成的配置方法,自动在属性名和其相应字段之间进行映射。我们所需要提供的只是属性前缀。

If you want to dig deeper into configuration properties, have a look at our in-depth article.


4.6. Alternative: YAML Files

4.6.替代方案 YAML文件

Spring also supports YAML files.


All the same naming rules apply for test-specific, environment-specific, and default property files. The only difference is the file extension and a dependency on the SnakeYAML library being on our classpath.


YAML is particularly good for hierarchical property storage; the following property file:


secret: foo

is synonymous with the following YAML file:


  url: jdbc:postgresql:/localhost:5432/instance
  username: foo
  password: bar
secret: foo

It’s also worth mentioning that YAML files do not support the @PropertySource annotation, so if we need to use this annotation, it would constrain us to using a properties file.


Another remarkable point is that in version 2.4.0 Spring Boot changed the way in which properties are loaded from multi-document YAML files. Previously, the order in which they were added was based on the profile activation order. With the new version, however, the framework follows the same ordering rules that we indicated earlier for .properties files; properties declared lower in the file will simply override those higher up.

另一个值得注意的地方是,在2.4.0版本中,Spring Boot改变了从多文档YAML文件加载属性的方式。以前,它们被添加的顺序是基于配置文件的激活顺序。然而,在新版本中,框架遵循了我们之前为.properties文件指出的相同的排序规则;文件中较低位置声明的属性将简单地覆盖较高位置的属性。

Additionally, in this version profiles can no longer be activated from profile-specific documents, making the outcome clearer and more predictable.


4.7. Importing Additional Configuration Files


Prior to version 2.4.0, Spring Boot allowed including additional configuration files using the spring.config.location and spring.config.additional-location properties, but they had certain limitations. For instance, they had to be defined before starting the application (as environment or system properties, or using command-line arguments) as they were used early in the process.

在2.4.0版本之前,Spring Boot允许使用spring.config.locationspring.config.extra-location属性包括额外的配置文件,但它们有一定的限制。例如,它们必须在启动应用程序之前定义(作为环境或系统属性,或使用命令行参数),因为它们是在流程的早期使用的。

In the mentioned version, we can use the spring.config.import property within the or application.yml file to easily include additional files. This property supports some interesting features:

在提到的版本中,我们可以在 application.yml 文件中使用spring.config.import属性,以轻松包含其他文件。该属性支持一些有趣的功能。

  • adding several files or directories
  • the files can be loaded either from the classpath or from an external directory
  • indicating if the startup process should fail if a file is not found, or if it’s an optional file
  • importing extensionless files

Let’s see a valid example:


Note: here we formatted this property using line breaks just for clarity.


Spring will treat imports as a new document inserted immediately below the import declaration.


4.8. Properties From Command Line Arguments


Besides using files, we can pass properties directly on the command line:


java -jar app.jar --property="value"

We can also do this via system properties, which are provided before the -jar command rather than after it:


java"value" -jar app.jar

4.9. Properties From Environment Variables


Spring Boot will also detect environment variables, treating them as properties:

Spring Boot也会检测环境变量,把它们当作属性。

export name=value
java -jar app.jar

4.10. Randomization of Property Values


If we don’t want determinist property values, we can use RandomValuePropertySource to randomize the values of properties:



4.11. Additional Types of Property Sources


Spring Boot supports a multitude of property sources, implementing a well-thought-out ordering to allow sensible overriding. It’s worth consulting the official documentation, which goes further than the scope of this article.

Spring Boot支持众多的属性源,实现了深思熟虑的排序,以允许合理的重写。值得参考的是官方文档,它比本文的范围更深入。

5. Configuration Using Raw Beans — the PropertySourcesPlaceholderConfigurer

5.使用Raw Beans进行配置 – PropertySourcesPlaceholderConfigurer

Besides the convenient methods of getting properties into Spring, we can also define and regiter the property configuration bean manually.


Working with the PropertySourcesPlaceholderConfigurer gives us full control over the configuration, with the downside of being more verbose and most of the time, unnecessary.


Let’s see how we can define this bean using Java configuration:


public static PropertySourcesPlaceholderConfigurer properties(){
    PropertySourcesPlaceholderConfigurer pspc
      = new PropertySourcesPlaceholderConfigurer();
    Resource[] resources = new ClassPathResource[ ]
      { new ClassPathResource( "" ) };
    pspc.setLocations( resources );
    pspc.setIgnoreUnresolvablePlaceholders( true );
    return pspc;

6. Properties in Parent-Child Contexts


This question comes up again and again: What happens when our web application has a parent and a child context? The parent context may have some common core functionality and beans, and then one (or multiple) child contexts, maybe containing servlet-specific beans.


In that case, what’s the best way to define properties files and include them in these contexts? And how to best retrieve these properties from Spring?


We’ll give a simple breakdown.


If the file is defined in the Parent context:


  • @Value works in Child context: YES
  • @Value works in Parent context: YES
  • environment.getProperty in Child context: YES
  • environment.getProperty in Parent context: YES

If the file is defined in the Child context:


  • @Value works in Child context: YES
  • @Value works in Parent context: NO
  • environment.getProperty in Child context: YES
  • environment.getProperty in Parent context: NO

7. Conclusion


This article showed several examples of working with properties and properties files in Spring.


As always, the entire code backing the article is available over on GitHub.