spring 中各个配置文件的说明

（1）pom.xml

　　pom.xml文件是在整个项目下面，该xml的主要作用是：导入框架的jar包及其所依赖的jar包，导入的jar包是写在<dependencies></dependencies>中

<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>oracle.MavenPro</groupId>
  <artifactId>MyFirstPro</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <dependencies>
  <!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>5.1.1.RELEASE</version>
    </dependency>
  <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>5.1.1.RELEASE</version>
    </dependency>
  
  </dependencies>
</project>

（2）spring.xml

　　spring.xml是通过spring框架来创建对象，而不需要在类中创建对象。

下面通过一个简单的sayhello例子来说明：

定义一个接口   ISayHello 

package com.service;

public interface ISayHello {
    public void sayHello();
}

定义    接口ISayHello 的实现类　　SayHelloImple 

package com.service.imple;

import com.service.ISayHello;

public class SayHelloImple implements ISayHello{
    @Override
    public void sayHello() {
        System.out.println("hello!!!");
        
    }
}

通过spring.xml来实例化对象，其中class属性是实现类的全路径，id是实例化对象的别名（hello）。

<?xml version="1.0" encoding="UTF-8" ?>
<beans   xmlns="http://www.springframework.org/schema/beans" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://www.springframework.org/schema/beans 
         http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
     <bean id="hello" class="com.service.imple.SayHelloImple"></bean>
</beans>

其中下面这段代码是告诉spring，通过什么编码来解析<bean>

新建一个test类

package com.service;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.service.imple.SayHelloImple;

public class Test {
    public static void main(String[] args) {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("spring.xml");
         
        SayHelloImple sayhello =
             (SayHelloImple) context.getBean("hello");
        sayhello.sayHello();
        
    }

}

下面这段代码是加载　　spring.xml　　文件

ApplicationContext context =
                new ClassPathXmlApplicationContext("spring.xml");

下面代码是获取实例化的对象hello

SayHelloImple sayhello =
             (SayHelloImple) context.getBean("hello");

运行结果为：