Spring application (Examples)

POM

Create a project named hello-spring of pom.xmlthe following documents:

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.funtl</groupId>
    <artifactId>hello-spring</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.17.RELEASE</version>
        </dependency>
    </dependencies>
</project>

Core package : a major increase org.springframework: the Spring context- dependent

Creating an interface and implementation

Creating UserService Interface

package com.funtl.hello.spring.service;

public interface UserService {
    public void sayHi();
}

Creating achieve UserServiceImpl

package com.funtl.hello.spring.service.impl;

import com.funtl.hello.spring.service.UserService;

public class UserServiceImpl implements UserService {
    public void sayHi() {
        System.out.println("Hello Spring");
    }
}

Create a Spring configuration file

In src/main/resourcesCreating directory spring-context.xmlprofiles, from now instantiate the class work to the Spring container management (IoC), the configuration file as follows:

<?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.xsd">

    <bean id="userService" class="com.funtl.hello.spring.service.impl.UserServiceImpl" />
</beans>

<bean />：用于定义一个实例对象。一个实例对应一个 bean 元素。

id：该属性是 Bean 实例的唯一标识，程序通过 id 属性访问 Bean，Bean 与 Bean 间的依赖关系也是通过 id 属性关联的。

class：指定该 Bean 所属的类，注意这里只能是类，不能是接口。

测试 Spring IoC

创建一个 MyTest 测试类，测试对象是否能够通过 Spring 来创建，代码如下：

package com.funtl.hello.spring;

import com.funtl.hello.spring.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    public static void main(String[] args) {
        // 获取 Spring 容器
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-context.xml");
        
        // 从 Spring 容器中获取对象
        UserService userService = (UserService) applicationContext.getBean("userService");
        userService.sayHi();
    }
}