Spring Boot参考指南

￡神魔★判官ぃ 2022-06-16 00:43 184阅读 0赞

*  IV Spring Boot 特性
    
     *  外部配置
        
         *  1 Configuring random values
         *  2 Accessing command line properties
         *  3 Application property files
         *  4 Profile-specific properties
         *  5 占位符 in properties
         *  6 Using YAML instead of Properties
            
             *  61 Loading YAML
             *  62 Exposing YAML as properties in the Spring Environment
             *  63 多种外形 YAML 文档

# IV. Spring Boot 特性 #

## 24. 外部配置 ##

Spring Boot 允许你进行显示配置，因此你可以使用相同的应用代码工作在不同的环境中。你可以使用properties文件，YAML文件，环境变量和命令行参数来显示配置。属性值可以直接使用@Value注解注释在bean上，通过Spring的环境抽象或者绑定到`@ConfigurationProperties`上。  
Spring Boot 使用 a very 特别的 `PropertySource` order that is 设计 to allow sensible overriding of values. Properties are considered in the following order:  
1. Devtools global settings properties on your home directory (~/.spring-boot-devtools.properties when devtools is active).  
@TestPropertySource annotations on your tests.  
@SpringBootTest\#properties annotation attribute on your tests.  
Command line arguments.  
Properties from SPRING\_APPLICATION\_JSON (inline JSON embedded in an environment variable or system property)  
ServletConfig init parameters.  
ServletContext init parameters.  
JNDI attributes from java:comp/env.  
Java System properties (System.getProperties()).  
OS environment variables.  
A RandomValuePropertySource that only has properties in random.\*.  
Profile-specific application properties outside of your packaged jar (application-\{profile\}.properties and YAML variants)  
Profile-specific application properties packaged inside your jar (application-\{profile\}.properties and YAML variants)  
Application properties outside of your packaged jar (application.properties and YAML variants).  
Application properties packaged inside your jar (application.properties and YAML variants).  
@PropertySource annotations on your @Configuration classes.  
Default properties (specified using SpringApplication.setDefaultProperties).  
提供一个具体的例子, 假设 you develop a `@Component` that uses a `name` property:

import org.springframework.stereotype.*
    import org.springframework.beans.factory.annotation.*
    
    @Component
    public class MyBean { 
    
        @Value("${name}")
        private String name;
    
        // ...
    
    }

在你的应用类路径上 (例如，在你的jar里) you can have an `application.properties` that provides a sensible 默认的属性值 for `name`. 当运行在一个新环境中的时候, an application.properties can be provided outside of your jar that overrides the name; and for one-off testing, you can launch with a specific command line switch (e.g. java -jar app.jar –name=”Spring”).

### 24.1 Configuring random values ###

### 24.2 Accessing command line properties ###

### 24.3 Application property files ###

### 24.4 Profile-specific properties ###

### 24.5 占位符 in properties ###

### 24.6 Using YAML instead of Properties ###

YAML is a superset of JSON, and as such is a very convenient format for specifying hierarchical configuration data. The SpringApplication class will automatically support YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.  
*If you use ‘Starters’ SnakeYAML will be automatically provided via spring-boot-starter.*

#### 24.6.1 Loading YAML ####

Spring Framework 提供了两个适当的类， 他们可以被用来加载YAML documents. The `YamlPropertiesFactoryBean` will load YAML as `Properties` and the `YamlMapFactoryBean` will load YAML as a `Map`.  
例如, 如下所示的YAML文档:

environments:
        dev:
            url: http://dev.bar.com
            name: Developer Setup
        prod:
            url: http://foo.bar.com
            name: My Cool App

#### 24.6.2 Exposing YAML as properties in the Spring Environment ####

The `YamlPropertySourceLoader` 类 can be used to expose YAML as a `PropertySource` in the Spring `Environment`. This allows you to use the familiar `@Value` annotation with placeholders syntax to access YAML properties.

#### 24.6.3 多种外形 YAML 文档 ####

你可以详细说明多个的 profile-specific YAML documents 在单一的文件中通过使用 a `spring.profiles` 键 来表示 when the document applies. 例如:

server:
     address: 192.168.1.100 ---
    spring:
     profiles: development
    server:
     address: 127.0.0.1 ---
    spring:
     profiles: production
    server:
     address: 192.168.1.120

在上面的例子中, 如果 `development` 外形是有效的，那么`server.address` 属性将会是`127.0.0.1` . 如果 `development` 和 `production` 外形没有激活, 那么属性值就会是 `192.168.1.100`.  
The default profiles are activated if none are explicitly active when the application context starts. So in this YAML we set a value for security.user.password that is only available in the “default” profile: