spring boot学习(6)— 配置信息及其读取优先级

摘要：优先级如下使用文件使用文件，会根据以下目录去寻找，添加到中，优先级依次递增。目录下目录工程根目录工程跟目录下的目录加载顺序从优先级高的先加载。属性值怎么取优先级高的会覆盖优先级低的。但是在同等目录下，优先级高于文件的配置信息。

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).

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

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)

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)

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/

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/

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