Spring introduction and quick start

1. Spring overview

1.1 What is Spring

Spring is a hierarchical Java SE/EE application full-stack lightweight open source framework with
IoC (Inverse Of Control) and
AOP (Aspect Oriented Programming) as the core.

It provides many enterprise-level application technologies such as the presentation layer SpringMVC, the persistence layer Spring JDBCTemplate, and business layer transaction management. It can also integrate many famous third-party frameworks and class libraries in the open source world, gradually becoming the most used Java EE enterprise application open source framework

1.2 Advantages of Spring

Facilitate decoupling and simplify development

AOP programming support

Support for declarative transactions

Convenient program testing

1.3 Spring's architecture

2. Spring Quick Start

2.1 Spring program development steps

①Import the coordinates of the basic package developed by Spring

②Write Dao interface and implementation class

③Create Spring core configuration file

④ Configure UserDaoImpl in the Spring configuration file

⑤Use Spring's API to obtain Bean instance

2.2 Import the basic package coordinates developed by Spring

<properties>
	<spring.version>5.0.5.RELEASE</spring.version>
</properties>
<!--导入spring的context坐标，context依赖core、beans、expression-->
<dependencies> 
    <dependency>  
        <groupId>org.springframework</groupId> 
        <artifactId>spring-context</artifactId> 
        <version>${spring.version}</version>
    </dependency>
</dependencies>

2.3 Write Dao interface and implementation class

public interface UserDao {
    
      
    public void save();
}

public class UserDaoImpl implements UserDao {
    
      
        @Override  
        public void save() {
    
    
        	System.out.println("UserDao save method running....");
	}
}

2.4 Create Spring Core Configuration File

Create applicationContext.xml configuration file under the classpath (resources)

<?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">
</beans>

2.5 Configure UserDaoImpl in the Spring configuration file

<?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="userDao" class="com.itheima.dao.impl.UserDaoImpl"></bean>
</beans>

2.6 Use Spring's API to Obtain Bean Instances

@Test
public void test1(){
    
    
		ApplicationContext applicationContext = new  
             ClassPathXmlApplicationContext("applicationContext.xml");
             UserDao userDao = (UserDao) applicationContext.getBean("userDao");
             userDao.save();
 }