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：

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
• task接口
• 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

测试

启动该服务后，在浏览器中输入：，会得到如下响应：

{"id":1,"content":"hello, world!"}

在后台日志会看到：

run footask
run bartask