Spring通过名称获取Bean示例
摘要：本文主要演示通过继承自抽象类ApplicationObjectSupport获取Bean实例。
参考文档：
Spring在代码中获取bean的几种方式提到共有以下几种方式：
- 方法一：在初始化时保存ApplicationContext对象
- 方法二：通过Spring提供的utils类获取ApplicationContext对象
- 方法三：继承自抽象类ApplicationObjectSupport
- 方法四：继承自抽象类WebApplicationObjectSupport
- 方法五：实现接口ApplicationContextAware
- 方法六：通过Spring提供的ContextLoader
完整示例代码请参考：https://github.com/sxpujs/spring-cloud-examples/tree/master/rest-service
软件环境：
- 操作系统：MacOS Catalina 10.15.3
- JDK 13.0.2
- spring-boot-starter-parent: 2.2.5.RELEASE
- Maven: 3.6.3
目录：
文件布局
localhost:rest-service didi$ tree .
.
├── pom.xml
├── src
│ └── main
│ └── java
│ └── com
│ └── example
│ ├── RestServiceApplication.java
│ ├── controller
│ │ ├── Greeting.java
│ │ └── GreetingController.java
│ ├── service
│ │ ├── BarTask.java
│ │ ├── FooTask.java
│ │ └── Task.java
│ └── util
│ └── SpringContextHolder.java
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.example</groupId>
<artifactId>springcloud-parent</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<groupId>com.example</groupId>
<artifactId>rest-service</artifactId>
<version>1.0-SNAPSHOT</version>
<name>rest-service</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>13</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Task接口
文件路径：src/main/java/com/example/service/Task.java
package com.example.service;
public interface Task {
void execute();
}
Task实现类BarTask
文件路径：src/main/java/com/example/service/BarTask.java
package com.example.service;
import org.springframework.stereotype.Service;
@Service("barTask")
public class BarTask implements Task {
@Override
public void execute() {
System.out.println("Run BarTask");
}
}
Task实现类FooTask
文件路径：src/main/java/com/example/service/FooTask.java
package com.example.service;
import org.springframework.stereotype.Service;
@Service("fooTask")
public class FooTask implements Task {
@Override
public void execute() {
System.out.println("Run FooTask");
}
}
Spring上下文工具类（继承ApplicationObjectSupport）
文件路径：src/main/java/com/example/util/SpringContextHolder.java
package com.example.util;
import com.example.service.Task;
import org.springframework.context.support.ApplicationObjectSupport;
import org.springframework.stereotype.Component;
@Component
public class SpringContextHolder extends ApplicationObjectSupport {
public Task getTask(String beanName){
return super.getApplicationContext().getBean(beanName , Task.class);
}
}
用于测试的GreetingController
文件路径：src/main/java/com/example/controller/GreetingController.java
package com.example.controller;
import java.util.concurrent.atomic.AtomicLong;
import com.example.service.Task;
import com.example.util.SpringContextHolder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class GreetingController {
private static final String template = "Hello, %s!";
private final AtomicLong counter = new AtomicLong();
@Autowired
SpringContextHolder holder;
@GetMapping("/greeting")
public Greeting greeting(@RequestParam(value = "name", defaultValue = "World") String name) {
Task task1 = holder.getTask("fooTask");
Task task2 = holder.getTask("barTask");
task1.execute();
task2.execute();
return new Greeting(counter.incrementAndGet(), String.format(template, name));
}
}
其它如src/main/java/com/example/RestServiceApplication.java和src/main/java/com/example/controller/Greeting.java等文件请参考Github
测试
启动该服务后，在浏览器中输入：http://localhost:8080/greeting，会得到如下响应：
{"id":1,"content":"Hello, World!"}
在后台日志会看到：
Run FooTask
Run BarTask
