spring boot学习(6)— 配置信息及其读取优先级

2024年3月12日 120次阅读来源: 工号1024

1. `properties` 信息从哪里取

在不同的环境，我们需要使用不同的配置，Spring boot 已经提供了相关功能，可以是 properties 文件， yaml 文件或是命令行参数。优先级如下

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.
```
java -jar app.jar --name="Spring"
```
Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property).
- environment vaiable：SPRING_APPLICATION_JSON='{"acme":{"name":"test"}}' java -jar myapp.jar
- command line:
  - java -Dspring.application.json='{"name":"test"}' -jar myapp.jar
  - java -jar myapp.jar --spring.application.json='{"name":"test"}'
ServletConfig init parameters.
ServletContext init parameters.
JNDI attributes from java:comp/env.
Java System properties (System.getProperties()).
OS environment variables.

A RandomValuePropertySource that has properties only in random.*.

my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.uuid=${random.uuid}
my.number.less.than.ten=${random.int(10)}
my.number.in.range=${random.int[1024,65536]}

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 by setting SpringApplication.setDefaultProperties).

2. 使用 `application.properties` 文件

使用 properties 文件，spring boot 会根据以下目录去寻找，添加到 Spring Environment 中，优先级依次递增。

classpath:/: resources 目录
classpath:/config/: resources 下 config 目录
file:./：工程根目录
file:./config/: 工程跟目录下的 config 目录

2.1 加载顺序：

从优先级高的先加载。

file:./config/
file:./
classpath:/config/
classpath:/

2019-03-27 22:38:24.848 DEBUG 39802 --- [           main] o.s.boot.SpringApplication               : Loading source class com.example.exitcode.DemoApplication
2019-03-27 22:38:24.915 DEBUG 39802 --- [           main] o.s.b.c.c.ConfigFileApplicationListener  : Loaded config file 'file:./config/application.properties' (file:./config/application.properties)
2019-03-27 22:38:24.915 DEBUG 39802 --- [           main] o.s.b.c.c.ConfigFileApplicationListener  : Loaded config file 'file:./application.properties' (file:./application.properties)
2019-03-27 22:38:24.915 DEBUG 39802 --- [           main] o.s.b.c.c.ConfigFileApplicationListener  : Loaded config file 'jar:file:xxxxx-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/config/application.properties' (classpath:/config/application.properties)
2019-03-27 22:38:24.915 DEBUG 39802 --- [           main] o.s.b.c.c.ConfigFileApplicationListener  : Loaded config file 'jar:file:xxxxx-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/application.properties' (classpath:/application.properties)

2.2 属性值怎么取

优先级高的会覆盖优先级低的。

./config/application.properties

testconfig.first=./config/
#testconfig.second=./config/
#testconfig.third=./config/
#testconfig.fourth=./config/

./application.properties

testconfig.first=./
testconfig.second=./
#testconfig.third=./
#testconfig.fourth=./

classpath:/config/application.properties

testconfig.first=classpath/config/
testconfig.second=classpath/config/
testconfig.third=classpath/config/
#testconfig.fourth=classpath/config/

classpath:/application.properties

testconfig.first=classpath
testconfig.second=classpath
testconfig.third=classpath
testconfig.fourth=classpath

输出如下：

2019-03-27 23:29:12.434  INFO 1335 --- [           main] com.example.properties.DemoApplication   : No active profile set, falling back to default profiles: default
first: ./config/
second: ./
third: classpath/config/
fourth: classpath
2019-03-27 23:29:13.052  INFO 1335 --- [           main] com.example.properties.DemoApplication   : Started DemoApplication in 16.565 seconds (JVM running for 23.467)

2.3 多环境配置文件

加一个文件： classpath:/application-product.properties

testconfig.first=product-classpath
testconfig.second=product-classpath

通过 spring.profiles.active 来指定环境所对应的 properties 文件：
运行 java -jar build/libs/properties-0.0.1-SNAPSHOT.jar --spring.profiles.active=product, 输出如下：

2019-03-28 20:34:44.726  INFO 25859 --- [           main] com.example.properties.DemoApplication   : The following profiles are active: product
first: product-classpath
second: product-classpath
third: classpath/config/
fourth: classpath
fifth: ./config/
sixth: ./config/
seventh: ./config/
eightth: ./config/

2.3 使用 `yaml` 文件来代替 `properties` 文件。

也可以使用 yaml 格式的文件。但是在同等目录下，properties 优先级高于 yaml 文件的配置信息。

新增文件 ./config/application.yml

testconfig:
  frist: ./config/yml
  second: ./config/yml

命令 java -jar build/libs/properties-0.0.1-SNAPSHOT.jar 输出为:

first: ./config/
second: ./config/yml
third: classpath/config/
fourth: classpath
fifth: ./config/
sixth: ./config/
seventh: ./config/
eightth: ./config/

2.5 属性文件中可以使用变量已经声明过的变量值：

app.name=MyApp
app.description=${app.name} is a Spring Boot application

    原文作者：工号1024
    原文地址: https://segmentfault.com/a/1190000018714698
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1. properties 信息从哪里取

2. 使用 application.properties 文件