Spring Boot Auto Configuration instance

Spring boot is able to automatically configure beans through the ability to configure beans based on conditions.

The commonly used conditions are as follows

2. @ConditionalOnBean: When the specified bean is present in the container

4. @ConditionalOnClass: Under the condition that the specified class exists under the current class path

6. @ConditionalOnExpression: Based on spel expression as the judging condition

8. @ConditionalOnJava: Based on the JVM version as the judging condition

10. @ConditionalOnJndi: Finds the specified location under the condition of Jndi presence

12. @ConditionalOnMissingBean: When the container does not have the specified bean condition

14. @ConditionalOnMissingClass: Under the condition of the current class path without the specified class

16. @ConditionalOnNotWebApplication: The current project is not under the condition of a Web project

18. @ConditionalOnProperty: Specifies whether the property has the specified value under conditions

20. @ConditionalOnResource: Whether there is a specified value under the Classpath

22. @ConditionalOnSingleCandidate: Specifies that the bean has only one in the container, or although there are multiple but specified preferred beans

24. @ConditionalOnWebApplication: The current project is under the condition of a Web project

These annotations all combine @conditional annotations, but use different conditions.

Next we write an automatic configuration and encapsulate it into starter pom.

First create a MAVEN project and import the following dependencies:

<dependency> <groupId>org.springframework.boot</groupId> <artifactId> Spring-boot-autoconfigure</artifactid> <version>1.3.8.RELEASE</version> </dependency>

The engineering structure is as follows

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Create Authorproperties class as a carrier of configuration information

package com.springboot.springboot_starter_hello;import  Org.springframework.boot.context.properties.ConfigurationProperties, @ConfigurationProperties (prefix= "author")/ /Specifies the prefix of the configuration content Public class authorproperties {private static final string name  =  "Weibo blog";p rivate static final int age = 18;private string  name = name;//default to micro-blog private int age = age;//default to 18public string  GetName ()  {return name;} Public void setname (String name)  {this.name = name;} Public int getage ()  {return age;} Public void setage (Int age)  {this.age = age;}}

package com.springboot.springboot_starter_hello;public class authorservice {private  String name;private int age;public string who () {return  "Name:" +name+ ", Age:" +age;} Public string getname ()  {return name;} Public void setname (String name)  {this.name = name;} Public int getage ()  {return age;} Public void setage (Int age)  {this.age = age;}} 

Create configuration class Authorserviceautoconfiguration, responsible for configuring bean

package com.springboot.springboot_starter_hello;import  org.springframework.beans.factory.annotation.autowired;import  org.springframework.boot.autoconfigure.condition.conditionalonclass;import  org.springframework.boot.autoconfigure.condition.conditionalonmissingbean;import  org.springframework.boot.autoconfigure.condition.conditionalonproperty;import  org.springframework.boot.context.properties.enableconfigurationproperties;import  org.springframework.context.annotation.bean;import org.springframework.context.annotation.configuration;@ configuration//declares the configuration class @enableconfigurationproperties (Authorproperties.class) @ConditionalOnClass ( Authorservice.class)//class path exists under the condition of AuthorService class @conditionalonproperty (prefix= "Author", value= "enabled", Matchifmissing=true)//In the case where the prefix author is configured to Enabled, that is, author=enabled, no configuration defaults to enabledpublic class  authorserviceautoconfiguration {@Autowiredprivate  authorproperties authorproperties;@ Bean@conditionalonmissingbeAn (Authorservice.class)//container with no AuthorService beans configured under the condition of the Beanpublic authorservice authorservice () { Authorservice authorservice = new authorservice (); Authorservice.setname ( Authorproperties.getname ()); Authorservice.setage (Authorproperties.getage ()); return authorservice;}}

If you want automatic configuration to take effect, you need to register the automatic configuration class. Create the Meta-inf/spring.factories file under Src/main/resources and write the following:

Org.springframework.boot.autoconfigure.enableautoconfiguration=com.springboot.springboot_starter_hello. Authorserviceautoconfiguration

If there are multiple auto-configuration classes, the "," is separated, where "\" is to be able to read the property after a newline.

Perform maven install after the above operation is complete.

The dependency is then introduced in the Spring Boot project:

<dependency><groupid>com.springboot</groupid><artifactid>springboot-starter-hello</ Artifactid><version>0.0.1-snapshot</version></dependency>

New AutoConfig class:

package com.springboot.autoconfig;import org.springframework.beans.factory.annotation.autowired; import org.springframework.boot.springapplication;import  org.springframework.boot.autoconfigure.springbootapplication;import  org.springframework.web.bind.annotation.requestmapping;import  Org.springframework.web.bind.annotation.restcontroller;import com.springboot.springboot_starter_hello. AuthorService, @SpringBootApplication @restcontrollerpublic class autoconfig {@Autowiredprivate  AuthorService authorService; @RequestMapping ("/") public string who () {return  Authorservice.who ();} Public static void main (String[] args)  {springapplication.run (AutoConfig.class,  args);}}

Run the class, Access localhost:8080, and the following results appear: Name: Weibo blog, age:18

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Next, create a new application.properties file under Src/main/resources and write the following:

Author.name=weareauthor.age=19

Rerun AutoConfig class: Name:weare,age:19

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Spring Boot Auto Configuration instance