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Spring通过名称获取Bean示例

2020-03-27 16:06:25来源：博客园阅读 ()

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：

Building a RESTful Web Service
Spring在代码中获取bean的几种方式

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

文件布局
pom.xml
Task接口
- Task实现类BarTask
- Task实现类FooTask
Spring上下文工具类（继承ApplicationObjectSupport）
用于测试的GreetingController
测试

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