Spring boot external configuration of the most complete analysis!

Tian Qiao Ba Xia 2020-11-10 15:38:16
spring boot external configuration complete

SpringBoot Configuration resolution in 【Externalized Configuration】

The main point of this article is

  • Introduce the priority of various configuration methods .
  • Introduce various external configuration methods .
  • Introduce yaml Format and principle of .
  • Describes how to bind and test type safe property configuration .
  • Introduce @ConfigurationProperties And @Value The difference between .

One 、SpringBoot The introduction and function order of external configuration in official documents

SpringBoot Support multiple external configurations , In order to facilitate developers in different environments , Use the same set of application code . There are many ways to externalize configuration :properties file ,yaml file ,Environment Variables, command line parameters, etc .

Attribute values of externalized configuration can be accessed through @Value Annotations are automatically injected , It can also be passed Spring Of Environment Abstract access , It can also be done through @ConfigurationProperties Annotations are bound to structured objects .

SpringBoot Support many kinds of external configuration , We will introduce to you later . before this , We have to know that if multiple configurations appear at the same time , It must take effect in a certain order . The following rules :

  1. devtool be in active In the state of ,$HOME/.config/spring-boot In the directory Devtool Global configuration .
  2. In the test @TestPropertySource annotation .
  3. In the test @SpringBootTest#properties Annotation features .
  4. Command line arguments .
  5. SPRING_APPLICATION_JSON Properties in ( Inline in environment variables or system properties JSON The embedded ).
  6. ServletConfig Initialize parameters .
  7. ServletContext Initialize parameters .
  8. java:comp/env Inside JNDI attribute
  9. JVM System attribute System.getProperties().
  10. Operating system environment variables
  11. Only with random.* Attribute RandomValuePropertySource .
  12. Outside of the app application-{profile}.properties perhaps application-{profile}.yml file
  13. Packaged in an application application-{profile}.properties perhaps application-{profile}.yml file
  14. Outside of the app application.properties perhaps appliaction.yml file
  15. Packaged in an application application.properties perhaps appliaction.yml file
  16. @Configuration On the class @PropertySource annotation , We need to pay attention to , stay ApplicationContext Before refreshing , The properties in this class will not be added to the environment , image logging.*,spring.main.* Something like that , It's too late to configure here .
  17. The default attribute ( adopt SpringApplication.setDefaultProperties Appoint ).

Here the list is sorted by group priority , in other words , Any property set in a high priority attribute source will override the same attribute with a lower priority , Columns like the command-line properties we mentioned above override application.properties Properties of .

Let's give you an example :

If in application.properties Set in name= God, jojobasha , At this point, I use the command line to set java -jar hyh.jar --author.name=summerday, The final name The value will be summerday, Because command line properties have a higher priority .

Two 、 Various external configurations

1、 Random value configuration

In profile ${random} Can be used to generate various types of random values , This simplifies the trouble of code generation , for example Generate int value 、long Value or string character string . The principle is ,RandomValuePropertySource Class overridden getProperty Method , Judge by random. After the prefix , It was properly handled .


2、 Command line parameter configuration

By default ,SpringApplication Set all command line option parameters 【 With -- Parameters at the beginning , Such as --server.port=9000】 Convert to properties , And add them to SpringEnvironment in , The configuration of command-line properties always takes precedence over other attribute configurations .

If you don't want to add command line properties to Environment in , have access to SpringApplication.setAddCommandLineProperties(false) Disable it .

$ java -jar app.jar --debug=true # Turn on debug Pattern , This is in application.properties The document defines debug=true It's the same

3、 Property file configuration

This part of property file configuration is familiar to us , We are creating... Quickly SpringBoot When the project is , The default will be resources Create one in the directory application.properties file .SpringApplication Will load the configuration properties from the configuration file , And finally join in Spring Of Environment in . except resources Under the table of contents , There are other paths ,SpringBoot By default, it supports storing configuration files .

  1. In the root directory of the current project /config Under the table of contents
  2. The root directory of the current project
  3. resources In the catalog /config Under the table of contents
  4. resources Under the table of contents

The four above , The priority goes down from top to bottom , in other words , If it appears at the same time , The properties configured above will override the following .

About profiles ,properties and yaml The files can meet the needs of the configuration .

Of course , These configurations are flexible , If you don't like the default profile name or the default path , You can configure it :

$ java -jar myproject.jar --spring.config.name=myproject
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties

4、 Appoint profile attribute

Usually , The applications we develop need to be deployed to different environments , The configuration of attributes naturally needs to be different . If you replace the configuration file every time you publish , Too much trouble .SpringBoot This is facilitated by the multi environment configuration of . The specific methods are as follows :

We said before when we introduced the priority of various configurations ,application-{profile}.properties perhaps application-{profile}.yml file Has a higher priority than application.properties or application.yml To configure , there profile It's the environmental identity we define :

We are resource Create three files in the directory :

  • application.properties: Default configuration ,default.
  • application-dev.properties: development environment ,dev.
  • application-prod.properties: Production environment ,prod.

We can do this by specifying spring.profiles.active Property to activate the corresponding configuration environment :


Or use the configuration form of command line parameters :

$ java -jar hyh.jar --spring.profiles.active=dev

without profile The specified file is in profile The configuration properties of the specified file are defined at the same time , The specified profile Configuration priority .

5、 Use placeholders

In the use of application.properties When it's worth , They're going to start from Environment Get the value , That means , You can refer to previously defined values , For example, reference to system properties . The specific methods are as follows :

name= God, jojobasha
description=${name} is my name

6、 Encrypt properties

Spring Boot Does not provide any built-in support for encrypted property values , however , It provides modify Spring Values in the environment The required hook point . We can do that by implementing EnvironmentPostProcessor Interface manipulates before the application starts Environment.

You can refer to howto.html, See how to use it .

7、 Use YAML Instead of properties

YAML yes JSON Superset , It's a kind of Specifies a convenient format for the hierarchy configuration data , We use properties A comparison of the documents shows that :

# yml
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8
username: root
password: 123456
- www.hyh.com
- www.yhy.com

As long as you have SnakeYAML library ,SpringApplication Class will automatically support YAML As a way to configure properties .SpringBoot In the project spring-boot-starter Related class libraries have been provided :org.yaml.snakeyaml, therefore SpringBoot Nature supports this way of configuration .

About yaml File format , Please refer to the official documents :Using YAML Instead of Properties

8、 Type safe property configuration

It's about passing @Value("${property}") Annotations to inject configuration can be cumbersome , Especially when multiple attributes are essentially hierarchical .SpringBoot It provides a solution : Let strong type bean Manage and verify your configuration .

Let's look directly at the specific use of the bell :

@ConfigurationPropertie Define a binding configuration of JavaBean

  1. Use the default constructor +getter and setter Inject
public class AcmeProperties {
private boolean enabled; //acme.enabled The default is false
private InetAddress remoteAddress;// acme.remote-address It can be downloaded from String The type of conversion
private final Security security = new Security();
//.. Omit getter and setter Method
public static class Security {
private String username; // acme.security.username
private String password; // acme.security.password
private List<String> roles = new ArrayList<>(Collections.singleton("USER"));// acme.security.roles
//.. Omit getter setter Method

This depends on the default null constructor , adopt getter and setter Method assignment , therefore getter and setter Methods are necessary , It does not support binding of static properties .

If nested pojo Property has been initialized with value : private final Security security = new Security(); No need setter Method . If you want the binder to create instances dynamically using its default constructor , You need to setter.

  1. adopt @ContructorBinding Annotations use constructor binding :
@ConstructorBinding // Annotations are bound with constructors
public class AcmeProperties {
private final Security security;
private final boolean enabled;
private final InetAddress remoteAddress;
public AcmeProperties(boolean enabled, InetAddress remoteAddress, Security security) {
this.enabled = enabled;
this.remoteAddress = remoteAddress;
this.security = security;
//.. Omit getter Method
public static class Security {
private final String username;
private final String password;
private final List<String> roles;
public Security(String username, String password,
@DefaultValue("USER") List<String> roles) {
this.username = username;
this.password = password;
this.roles = roles;
//.. Omit getter Method

If not configured Security Instance attributes , So the final result :Security=null. If we want to Security={username=null,password=null,roles=[USER]}, Can be in Security Add up @DefaultValue.public AcmeProperties(boolean enabled, InetAddress remoteAddress, @DefaultValue Security security)

adopt @EnableConfigurationProperties register

It's already defined JavaBean, And bind with configuration properties , Then you need to register these bean. We usually use @Component or @Bean,@Import load bean It's not advisable here ,SpringBoot Provides a solution : Use @EnableConfigurationProperties, We can specify the configured classes one by one , It can also be configured as a component scan .

@EnableConfigurationProperties({HyhConfigurationProperties.class, MyProperties.class,AcmeProperties.class})
public class SpringBootProfileApplication {
public class SpringBootProfileApplication {

To configure yaml file

username: admin

Inject properties, test

public class Application implements CommandLineRunner {
private AcmeProperties acmeProperties;
public void run(String... args) throws Exception {
// Output :
AcmeProperties(security=AcmeProperties.Security(username=admin, password=null, roles=[USER, ADMIN]), enabled=false, remoteAddress=/

Loose binding

SpringBoot Adopt loose rules Environment and @ConfigurationProperties mark bean The matching of . Such as :

public class OwnerProperties {
private String firstName;
public String getFirstName() {
return this.firstName;
public void setFirstName(String firstName) {
this.firstName = firstName;

The attribute names in the following table can match :

Property Note
acme.my-project.person.first-name Kebab case, which is recommended for use in .properties and .yml files.
acme.myProject.person.firstName Standard camel case syntax.
acme.my_project.person.first_name Underscore notation, which is an alternative format for use in .properties and .yml files.
ACME_MYPROJECT_PERSON_FIRSTNAME Upper case format, which is recommended when using system environment variables.

@ConfigurationProperties In the annotations prefix The value must be kebab case Formal , With - For the separator .

Spring The official advice , Properties as much as possible lower-case kebab In the form of :my.property-name=acme

Map How to bind

Bound to the Map Attribute , If key contain Lower case alphanumeric characters or - Any other characters other than , You need to use square brackets around key, In order to keep the original value . If the key is not [] Surround , Then all non alphanumeric or - The characters of will be deleted . as follows :

username: God, jojobasha
password: 123456
"[/key1]": value1 # Surround with quotation marks [], use [] Surround key
/key3: value3
key-4: value4
key/5: value5
# result :"map":{/key1=value1,key5=value5, key-4=value4, key3=value3}

How environment variables bind

Follow three principles :

  1. hold . Change to underline _.
  2. remove -.
  3. Small to capital .

Such as :spring.main.log-startup-info To :SPRING_MAIN_LOGSTARTUPINFO,my.acme[0].other To MY_ACME_0_OTHER.

9、 Complex type

Previous introduction yml file , This paper introduces the simple binding of array form or value ,SpringBoot It also supports binding of complex types .

- name: God, jojobasha
desc: Handsome
- name: tqbx
desc: It's so handsome
name: summerday
desc: handsome!
name: summer
@ConfigurationProperties(prefix = "merge")
public class MergeProperties {
private final List<User> list = new ArrayList<>();
private final Map<String,User> map = new HashMap<>();
public List<User> getList() {
return list;
public Map<String, User> getMap() {
return map;

The final output :

list=[User(name= God, jojobasha , desc= Handsome ),
User(name=tqbx, desc= It's so handsome )],
map={key1=User(name=summerday, desc=handsome!),
key2=User(name=summer, desc=null)}a

10、 Parameter checking

Yes @ConfigurationProperties Class uses Spring Of @Valid When the annotation ,Spring Boot They try to verify it .

You can use it directly on the configuration class JSR-303 javax.validation constraint annotation . The premise of this is , Your classpath has compatible JSR-303 Realization :


Then add the constraint annotation to the field , as follows :

@ConfigurationProperties(prefix = "validate")
public class ValidateProperties {
private String name;
private final SubProperties subProperties = new SubProperties();
public static class SubProperties {
@Min(value = 10,message = " The youngest is 10")
public Integer age;

The configuration is as follows :

name: hyh
age: 5

give the result as follows :

Binding to target org.springframework.boot.context.properties.bind.BindException:
Failed to bind properties under 'validate' to com.hyh.config.ValidateProperties failed:
Property: validate.sub-properties.age
Value: 5
Origin: class path resource [application.yml]:47:10
Reason: The youngest is 10
Update your application's configuration

3、 ... and 、@ConfigurationProperties And @Value The difference between

@Value Annotation is a core container function , It is not provided and type-safe Configuration properties related functions , The following table summarizes the functions supported by each :

Feature @ConfigurationProperties @Value
Loose binding Yes Limited (see note below)
Metadata support Yes No
SpEL expression No Yes

The official advice :

  • If you define a set of configurations for your components , It is recommended to use @ConfigurationProperties and POJO binding , This provides structured and type safe objects .
  • If you have to use it hard @Value, It is recommended to use kebab-case form , Such as @Value(" ${demo.item-price}")

Source download

The content of this article is a summary of excellent blogs and official documents , The address of the original text has been marked in the reference section of the text . Last , All the code samples in this article have been uploaded to Gitee:https://gitee.com/tqbx/springboot-samples-learn, There are other SpringBoot The integration of oh .

Reference reading

本文为[Tian Qiao Ba Xia]所创,转载请带上原文链接,感谢

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