@How can conditionalonmissingbean cover beans in third-party components

1. Customize a simple  spring-boot Components

• establish  olive-starter project

Corresponding pom.xml The documents are as follows

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.olive</groupId>
  <artifactId>olive-starter</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.7.1</version>
    <relativePath/>
  </parent>
  <name>olive-starter</name>
  <description>olive starter for Spring Boot</description>
  <properties>
    <java.version>1.8</java.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </dependency>
  </dependencies>
</project>

Be careful not to introduce spring-boot Plug in for , Use maven Native , Otherwise use maven  install When the , Other projects cannot be introduced

• Define an interface for loading routes

package com.olive.service;
import java.util.List;
import com.olive.model.RouterDO;


public interface RouterService {
  public List<RouterDO> getRouters();
}

Entity class of route DouterDO And implementation classes are as follows

DouterDO.java class

package com.olive.model;


import java.io.Serializable;


public class RouterDO implements Serializable{
  
  private String id;
  
  private String routerName;
  
  //TODO  Omit getter  setter
}

DefaultRouterServiceImpl.java class , Default route loading policy

package com.olive.service.impl;


import java.util.ArrayList;
import java.util.List;
import com.olive.model.RouterDO;
import com.olive.service.RouterService;


public class DefaultRouterServiceImpl implements RouterService{


  @Override
  public List<RouterDO> getRouters() {
    //TODO
     System.out.println("-------------DefaultRouterServiceImpl----------");
    return new ArrayList<RouterDO>();
  }


}

• Configure the default route loading Bean
  

package com.olive.config;


import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.olive.service.RouterService;
import com.olive.service.impl.DefaultRouterServiceImpl;


@Configuration
public class RouterConfig {


  @Bean
    @ConditionalOnMissingBean
    public RouterService getRouterService(){
        return new DefaultRouterServiceImpl();
    }


}

establish MATE-INF Folder , And create... Under this file spring.factories file ;spring.factories The contents of the document are as follows

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.olive.config.RouterConfig

The overall project structure is as follows ：

2.  Create another project olive-gateway, quote  olive-starter engineering

• olive-gateway Of pom.xml The documents are as follows

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.olive</groupId>
  <artifactId>olive-gateway</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.7.1</version>
    <relativePath />
  </parent>
  <name>olive-starter</name>
  <description>olive starter for Spring Boot</description>
  <properties>
    <java.version>1.8</java.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
      <groupId>com.olive</groupId>
      <artifactId>olive-starter</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>
  </dependencies>
</project>

• establish springboot Start the boot class
  

package com.gateway;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import com.olive.service.RouterService;


@SpringBootApplication
public class GwApplication {


  public static void main(String[] args) {
    ApplicationContext ac = SpringApplication.run(GwApplication.class, args);
    RouterService routerService = ac.getBean(RouterService.class);
    routerService.getRouters();
  }
  
}

Start project

Watch the log , Use the default route loading class  DefaultRouterServiceImpl

• Then customize a route loading class implementation  RouterService Interface

package com.gateway.service.impl;


import java.util.ArrayList;
import java.util.List;
import org.springframework.stereotype.Service;
import com.olive.model.RouterDO;
import com.olive.service.RouterService;




@Service
public class CustomRouterServiceImpl implements RouterService {
  @Override
  public List<RouterDO> getRouters() {
    System.out.println("-------CustomRouterServiceImpl------");
    return new ArrayList<>();
  }
}

Restart the project

Watch the log , The default route loading class has been overridden  DefaultRouterServiceImpl

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