Notes on springboot configuration file, annotation and automatic configuration principle (1)

European Union 2020-11-09 07:35:33
notes springboot configuration file annotation

One 、springboot Simple operation principle of

First ,springboot There must be a parent project , Namely maven Medium pom The


Click the parent file launcher , It's mainly made up of a lot of dependencies


He came to really manage Spring Boot All dependent versions in the application ;

It's also called Spring Boot Version of the Arbitration Center , There are a lot of definitions in it springboot The version of the dependent package introduced by the parent file -properties;

In the future, we import dependency by default and do not need to write version ;( Not in the dependencies The dependency of internal management naturally needs to declare version number )

quite a lot springboot Rely on the jar Packages are packaged into many initiators according to the application situation and function , Such as web starter , I'll introduce web starter


spring-boot-starter:spring-boot Scene launcher ; Helped us import web The components that the module depends on for normal operation ;
Spring Boot Extract all functional scenarios , Make one by one starters( starter ), Just introduce these... Into the project starter
All dependencies of related scenarios will be imported . You can import the initiator of any scene with any function

Main startup class

 *  @SpringBootApplication  To mark a main program class , It shows that this is a Spring Boot application
public class HelloWorldMainApplication {
    public static void main(String[] args) {
        // Spring The app starts,args);

@SpringBootApplication: Spring Boot Apply annotation to a class to indicate that the class is SpringBoot The main configuration class of ,SpringBoot
You should run this class main Method to start SpringBoot application ;

@ComponentScan(excludeFilters = {
      @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
      @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {

@SpringBootConfiguration:Spring Boot Configuration class ;
Mark on a class , That means this is one Spring Boot Configuration class ;
@Configuration: This annotation is marked on the configuration class ;
Configuration class ----- The configuration file ; The configuration class is also a component in the container ;@Component

@EnableAutoConfiguration: Turn on the auto configuration function ;
What we need to configure before ,Spring Boot Help us automatically configure ;@EnableAutoConfiguration tell SpringBoot Open from
Dynamic configuration function ; In this way, the automatic configuration can take effect ;

public @interface EnableAutoConfiguration {

@AutoConfigurationPackage: Automatic configuration package
Spring The bottom notes @Import, Import a component into the container ; The imported components are created by

With the autoconfig class , It is unnecessary for us to write configuration injection function components manually ;
Spring Boot From the classpath at startup META-INF/spring.factories In order to get EnableAutoConfiguration The specified value , take
These values are imported into the container as autoconfig classes , The autoconfig class takes effect , Help us with automatic configuration ; We used to need our own configuration
In the west , Automatic configuration classes help us ;
J2EE The overall integration solution and automatic configuration of spring-boot-autoconfigure-1.5.9.RELEASE.jar;

The main configuration class (@SpringBootApplication Class marked ) All components in the package and all subpackages below are scanned to Spring Containers ;
Import components into the container ?
EnableAutoConfigurationImportSelector: Which component selectors to import ;
Returns all components that need to be imported as full class names ; These components are added to the container ;
A lot of autoconfig classes will be imported into the container (xxxAutoConfiguration); It is to import all the components needed for this scenario into the container ,
And configure these components ;

Two 、springboot Configuration file for

SpringBoot Use a global profile , The profile name is fixed ;

Role of profile : modify SpringBoot Default for auto configuration ;SpringBoot At the bottom, we'll configure it automatically ;

YAML(YAML Ain't Markup Language)
YAML A Markup Language: It's a markup language
YAML isn't Markup Language: It's not a markup language ;
Markup language :
Previous configuration files ; Most of them use xxxx.xml file ;
YAML: Data centric , Than json、xml And so on are more suitable for configuration files ;
YAML: Configuration example

  port: 8081 # Do not use tab Key indent , A colon followed by a space , Properties and values are case sensitive 

2、 How to write value
Literal : Normal value ( Numbers , character string , Boolean )
k: v: Write it literally ;
By default, strings do not need to be enclosed with single quotation marks or double quotation marks ;
"": Double quotes ; Does not escape special characters in a string ; Special characters will be used as the meaning they want to express
name: "zhangsan \n lisi": Output ;zhangsan Line break lisi
'': Single quotation marks ; Can escape special characters , The special character is only a common string data
name: ‘zhangsan \n lisi’: Output ;zhangsan \n lisi

object 、Map( Attributes and values )( Key value pair ):
k: v: On the next line, write the relationship between an object's properties and values ; Note that the indentation
The object is still k: v The way

lastName: zhangsan        
age: 20 

Inline writing

friends: {lastName: zhangsan,age: 18}

Array (List、Set):
use - Value represents an element in an array

 ‐ cat
 ‐ dog
 ‐ pig

Inline writing

pets: [cat,dog,pig]

3、 ... and 、springboot Profile Injection

    lastName: hello
    boss: false
    maps: {k1: v1,k212}
      ‐ lisi
      ‐ zhaoliu
      name:  puppy


 *  Set the value of each property configured in the configuration file , Map to this component
 * @ConfigurationProperties: tell SpringBoot Bind all the properties in this class with the relevant configuration in the configuration file ;
 *      prefix = "person": Which of the following attributes in the configuration file should be mapped one by one
 *  Only this component is the component in the container , Can be provided by the container @ConfigurationProperties function ;
@ConfigurationProperties(prefix = "person")
public class Person {
    private String lastName;
    private Integer age;
    private Boolean boss;
    private Date birth;
    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;

We can import the profile processor , You will be prompted to write the configuration later

<!‐‐ Import profile processor , You will be prompted when binding the configuration file ‐‐>

1、properties Configuration file in idea The default utf-8 It could be messy

2、@Value Get the value and @ConfigurationProperties Get value comparison

The configuration file yml still properties They all get value ;

if , We just need to get some value in the configuration file in some business logic , Use @Value;
if , We wrote a special javaBean To map with the configuration file , We'll just use it @ConfigurationProperties;

3、 Configuration file injection value data verification

@ConfigurationProperties(prefix = "person")
public class Person {
     * <bean class="Person">
     *      <property name="lastName" value=" Literal /${key} From environment variables 、 Get the value in the configuration file /#
     * <bean/>
   //lastName Must be in email format 
    private String lastName;
    private Integer age;
    private Boolean boss;
    private Date birth;
    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;

@PropertySource: Load the specified configuration file ;

 *  Set the value of each property configured in the configuration file , Map to this component
 * @ConfigurationProperties: tell SpringBoot Bind all the properties in this class with the relevant configuration in the configuration file ;
 *      prefix = "person": Which of the following attributes in the configuration file should be mapped one by one
 *  Only this component is the component in the container , Can be provided by the container @ConfigurationProperties function ;
 *  @ConfigurationProperties(prefix = "person") Get the value from the global configuration file by default ;
@PropertySource(value = {""})
@ConfigurationProperties(prefix = "person")
public class Person {
     * <bean class="Person">
     *      <property name="lastName" value=" Literal /${key} From environment variables 、 Get the value in the configuration file /#
     * <bean/>
   //lastName Must be in email format 
   // @Email
    private String lastName;
    private Integer age;
    private Boolean boss;

@ImportResource: Import Spring Configuration file for , Let the content in the configuration file take effect ;
Spring Boot There's no Spring Configuration file for , Our own configuration file , It doesn't automatically recognize ;
Want to make Spring The configuration file of is valid , Loading in ;@ImportResource Mark on a configuration class

@ImportResource(locations = {"classpath:beans.xml"})
Import Spring The configuration file for

Not to write Spring Configuration file for

<?xml version="1.0" encoding="UTF‐8"?>
<beans xmlns=""
    <bean id="helloService" class="com.atguigu.springboot.service.HelloService"></bean>

SpringBoot Recommended ways to add components to a container ; It is recommended to use full annotation
1、 Configuration class @Configuration------>Spring The configuration file
2、 Use @Bean Add components to the container

 * @Configuration: Indicates that the current class is a configuration class ; Is to replace the previous Spring The configuration file
 *  Use... In the configuration file <bean><bean/> Tag add components
public class MyAppConfig {
    // Add the return value of the method to the container ; This component in the container defaults to id It's the method name 
    public HelloService helloService02(){
        System.out.println(" Configuration class @Bean Added components to the container ...");
        return new HelloService();

4、 Placeholder for profile
1、 random number

person.last‐name= Zhang San ${random.uuid}

1、 many Profile file
When we write the main configuration file , The filename can be application-{profile}.properties/yml
By default Configuration of ;
2、yml Support multi document block mode

    active: prod
  profiles: dev
  profiles: prod  # Specify which environment 

3、 Activate assignment profile
1、 Specified in the configuration file
2、 Command line :
java -jar spring-boot-02-config-0.0.1-SNAPSHOT.jar;
You can test it directly , Configure the incoming command line parameters
3、 Virtual machine parameters ;

6、 Configuration file loading location

springboot Startup will scan the following locations perhaps application.yml File as Spring boot The default profile for
Pieces of
Priority from high to low , High priority configuration overrides low priority configuration ;
  port: 8081
    active: prod
  port: 8083
  profiles: dev
  port: 8084
  profiles: prod  # Specify which environment
SpringBoot The main configuration file will be loaded from all four locations ; Complementary configuration ;
We can also go through spring.config.location To change the default profile location
After the project is packaged , We can use the form of command line arguments , When starting a project, specify the new location of the configuration file ; Specify the configuration file and the default
Recognize that the loaded configuration files work together to form a complementary configuration ;
java -jar spring-boot-02-config-02-0.0.1-SNAPSHOT.jar --spring.config.location=G:/

7、 External configuration loading order

SpringBoot You can also load the configuration from ; Priority from high to low ; The high priority configuration covers the low priority configuration , All configurations will
Form complementary configuration
1. Command line arguments
All configurations can be specified on the command line
java -jar spring-boot-02-config-02-0.0.1-SNAPSHOT.jar --server.port=8087 --server.context-path=/abc
Multiple configurations are separated by spaces ; -- Configuration item = value
2. come from java:comp/env Of JNDI attribute
3.Java System attribute (System.getProperties())
4. Operating system environment variables
5.RandomValuePropertySource Configured random.* Property value
from jar Bag out jar Search inside the bag ;
Priority loading band profile
6.jar The outside of the bag application-{profile}.properties or application.yml( belt spring.profile) The configuration file
7.jar Inside the bag application-{profile}.properties or application.yml( belt spring.profile) The configuration file
Load again without profile
8.jar The outside of the bag or application.yml( No spring.profile) The configuration file
9.jar Inside the bag or application.yml( No spring.profile) The configuration file
[email protected] On the annotation class @PropertySource
11. adopt SpringApplication.setDefaultProperties Default properties specified
All supported configuration loading sources ;

8、 Auto configuration principle

What the configuration file can write ? How to write ? Auto configuration principle ;

1、 Auto configuration principle :
1)、SpringBoot Load the main configuration class at startup , Automatic configuration is enabled @EnableAutoConfiguration
2)、@EnableAutoConfiguration effect :
utilize EnableAutoConfigurationImportSelector Import some components into the container ?
You can see selectImports() Contents of the method ;
List configurations = getCandidateConfigurations(annotationMetadata, attributes); Get the candidate configuration

Every one of these xxxAutoConfiguration Class is a component of a container , All added to container ; Use them for automatic configuration ;
3)、 Each auto configuration class can be configured automatically ;
4)、 With HttpEncodingAutoConfiguration(Http Code auto configuration ) For example, explain the principle of automatic configuration ;

@Configuration   // Indicates that this is a configuration class , The configuration files written before are the same , You can also add components to the container 
@EnableConfigurationProperties(HttpEncodingProperties.class)  // Start... For the specified class 
ConfigurationProperties function ; Set the corresponding value in the configuration file with HttpEncodingProperties Bind up ; And put
HttpEncodingProperties Add to ioc In the container
@ConditionalOnWebApplication //Spring Bottom @Conditional annotation (Spring Annotated edition ), According to different conditions , If 
Meet the specified conditions , The configuration in the entire configuration class will take effect ;     Determine whether the current application is web application , If it is , The current configuration class takes effect
@ConditionalOnClass(CharacterEncodingFilter.class)  // Determine whether the current project has this class 
CharacterEncodingFilter;SpringMVC Filter to solve the garbled code in ;
@ConditionalOnProperty(prefix = "spring.http.encoding", value = "enabled", matchIfMissing =
true)  // Determine whether a configuration exists in the configuration file   spring.http.encoding.enabled; If it doesn't exist , Judgment is also true 
// Even if we don't configure pring.http.encoding.enabled=true, It also takes effect by default ;
public class HttpEncodingAutoConfiguration {
   // He has been with SpringBoot The configuration file of is mapped  
   private final HttpEncodingProperties properties;
// There is only one case where there is a parameter constructor , The value of the parameter is taken from the container 
   public HttpEncodingAutoConfiguration(HttpEncodingProperties properties) { = properties;        
    @Bean   // Add a component to the container , Some values for this component need to be from properties In order to get 
@ConditionalOnMissingBean(CharacterEncodingFilter.class) // Determine that the container does not have this component ?    
public CharacterEncodingFilter characterEncodingFilter() {    
CharacterEncodingFilter filter = new OrderedCharacterEncodingFilter();        
return filter;        

Judge according to different conditions , Determine whether the configuration class is effective ?
Once this configuration class takes effect ; This configuration class will add various components to the container ; The properties of these components are from the corresponding properties Get in class
Of , Each property in these classes is bound to the configuration file ;
5)、 All the properties that can be configured in the configuration file are in xxxxProperties Class ‘; The configuration file can refer to a certain function as long as it can be configured
The corresponding property class

@ConfigurationProperties(prefix = "spring.http.encoding")  // Get the specified values and... From the configuration file bean Of 
Sex binding
public class HttpEncodingProperties {
   public static final Charset DEFAULT_CHARSET = Charset.forName("UTF‐8");

quintessence :
1)、SpringBoot Startup loads a large number of autoconfig classes
2)、 Let's see if there are any functions we need SpringBoot Auto configuration class written by default ;
3)、 Let's see what components are configured in this auto configuration class ;( As long as the components we want to use are , We don't need to configure it again )
4)、 When adding components to the container's auto configuration class , From properties Class to get some properties . We can specify this in the configuration file
The value of some attributes ;
xxxxAutoConfigurartion: Automatic configuration class ;
Add components to the container

xxxxProperties: Encapsulate the properties in the configuration file ;
2、 details
1、@Conditional Derived annotations (Spring The annotated version is original @Conditional effect )
effect : Must be @Conditional The specified conditions hold , Add components to the container , All the contents in the configuration configuration will take effect ;

The autoconfig class can only take effect under certain conditions ;
How do we know which autoconfig classes work ;
We can use debug=true attribute ; To have the console print the autoconfiguration report , In this way, we can easily know which automatic configuration
Class effective ;

Positive matches:( Autoconfig class enabled )
   DispatcherServletAutoConfiguration matched:
    ‐ @ConditionalOnClass found required class
'org.springframework.web.servlet.DispatcherServlet'; @ConditionalOnMissingClass did not find
unwanted class (OnClassCondition)
      ‐ @ConditionalOnWebApplication (required) found StandardServletEnvironment
Negative matches:( Has not started , No autoconfig classes matched successfully )
      Did not match:
         ‐ @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory',
'org.apache.activemq.ActiveMQConnectionFactory' (OnClassCondition)
      Did not match:
         ‐ @ConditionalOnClass did not find required classes
'org.aspectj.lang.annotation.Aspect''org.aspectj.lang.reflect.Advice' (OnClassCondition)


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