Three minutes easy to understand Spring framework basics

As a qualified Java developer, you must have heard of the spring framework, though it will be applied, but it may not be able to understand the principles of the framework, but just like everyone else, the general just stays on the understanding level. The mini-series will take you through the spring framework with a step-by-step look.

Struts:web layer, relatively simple (valuestack value stack, interceptor);
Hibernate:dao layer, knowledge point Miscellaneous;
Spring:service layer, important, how much to say how much.

The architecture in mind:

I. Overview of the Spring framework

1.1 What is Spring

Spring is an open source framework, and spring is a lightweight Java development framework that emerged in 2003 by Rod Johnson in his book expert one-on-one development and Some of the concepts and prototypes elaborated in design are derived. It is created to address the complexities of enterprise application development. One of the main advantages of the framework is its layered architecture, which allows the user to choose which component to use, while providing an integrated framework for Java EE application development. Spring uses basic JavaBean to accomplish things that were previously only possible by EJBS. However, the use of spring is not limited to server-side development. From the standpoint of simplicity, testability, and loose coupling, any Java application can benefit from spring. The core of spring is control inversion (IoC) and facet-oriented (AOP). In short, spring is a layered javase/ee full-stack (one-stop) lightweight open-source framework.

• Lightweight: Compared to EJB, it relies on less resources and destroys less resources.

• Tiering: A one-stop solution for every layer

Web tier: STRUTS,SPRING-MVC
Service Layer: Spring
DAO Layer: Hibernate,mybatis, jdbctemplate–> Spring-data

1.2 Spring origin

• Expert one-to-one-ee Design and development

• Expert one-to-one EE development without EJB

1.3 Spring Core

The core of spring is control inversion (IoC) and aspect-oriented (AOP)

? 1.4 Spring Benefits

• Easy decoupling, simplified development (cohesion poly-low coupling)
  
  

• Spring is a large factory (container) that allows all object creation and dependency maintenance to be given to spring management

• Spring Factory is used to generate beans

Support for AOP programming

• Spring provides aspect-oriented programming, which can easily implement the functions of permission interception, operation monitoring, etc.

Support for declarative Transactions

• The management of transactions can be done only through configuration, without the need for manual programming

Easy testing of programs

• Spring support for JUNIT4, which can be easily tested with annotations for spring programs

Easy integration of a variety of excellent frameworks

• Spring does not exclude a variety of excellent open source frameworks that provide direct support for a variety of excellent frameworks (e.g. Struts, Hibernate, MyBatis, quartz, etc.)

Reduce the difficulty of using Java EE APIs

• Spring provides encapsulation for some of the most difficult APIs (JDBC, JavaMail, remote calls, and so on) in Java EE Development, making these API applications much less difficult to apply

? 1.5 Spring Architecture

The Spring framework is a layered architecture that eats a range of functional elements and is divided into about 20 modules. These modules are divided into Rore Container, Date access/integration, Web, AOP (Aspect oriented programming), instrumentation, and test sections, as shown in:

Core containers: beans, core, context, expression

Ii. Introductory Case: IoC "mastering" 2.1 Importing JAR Packages

4 + 1:4 cores (beans, core, context, expression) + 1 dependencies (Commons-loggins...jar)

? 2.2 Target Class

1. Provide UserService interface and implementation Class 2. Get an instance of the UserService implementation class

In the previous development, a direct new object can be.
After learning spring, the object instance will be created by spring –> IoC controlled inversion (inverse of control).
When you need an instance object later, from the Spring Factory (container), you need to configure the fully qualified name of the implementation class into an XML file.

UserService Interface:

• 1 public interface UserService {

• 2 public void AddUser ();

• 9 ·

Userserviceimpl Implementation class:

• 1 public class Userserviceimpl implements UserService {

• 2 @Override

• 3 public void AddUser () {

• 4 System.out.println ("A_ico add User");

• 5}

• 6}

? 2.3 Configuration file

• Location: arbitrary, under development in general under CLASSPATH (SRC)

• Name: Any, common applicationcontext.xml in development

• Content: Adding schema constraints

• Constraint file location: spring-framework-3.2.0.release\docs\spring-framework-reference\html\ xsd-config.html

Harbin Love still training-java

<?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 ">

<!--Configuring service

<bean> Configure the objects you want to create

ID: Used for subsequent instance acquisition from the Spring container.

Class: The fully qualified class name of the instance that needs to be created

-

<bean id= "Userserviceid" class= "COM.ITHEIMA.A_IOC. Userserviceimpl "></bean>

</beans>

? 2.4 Test

@Test

public void demo02 () {

Obtained from the spring container

1 Getting the container

String Xmlpath = "Com/itheima/a_ioc/beans.xml";

ApplicationContext ApplicationContext = new Classpathxmlapplicationcontext (Xmlpath);

2 Getting content-no need for yourself new, all from the spring container

UserService UserService = (userservice) applicationcontext.getbean ("Userserviceid");

Userservice.adduser ();

}

Iii. Introductory Case: DI "Mastery"

• DI Dependency Injection, Dependency injection
  is a: It is a, inherited.
  Has a: There is a, member variable, dependent.

Class B {

Private a A; Class B relies on Class A

}

Dependency: One object needs to use another object

Inject: Another object instance setting through the setter method.

• For example:

Class bookserviceimpl{

Previously developed: interface = Implementation Class (service and DAO coupling)

Private Bookdao Bookdao = new Bookdaoimpl ();

After spring (decoupling: the Service implementation class uses the DAO interface and does not know the specific implementation class)

Private Bookdao Bookdao;

Setter method

}

Simulating the spring execution process
1. Create service instance: Bookservice bookservice = new Bookserviceimpl () –>ioc <bean>
2. Create a DAO instance: Bookdao Bookdao = new Bookdaoimple () –>IOC
3. Set the DAO to Service:bookService.setBookDao (Bookdao); –>di<property>

3.1. Target class

· Creating Bookservice interfaces and implementing classes

· Creating Bookdao interfaces and implementing classes

· The DAO and service configuration XML files

· Using API Testing

3.1.1 DAO

Public interface Bookdao {

public void Addbook ();

}

public class Bookdaoimpl implements Bookdao {

@Override

public void Addbook () {

System.out.println ("di add book");

}

}

3.1.2 Service

Public interface Bookservice {

public abstract void Addbook ();

}

public class Bookserviceimpl implements Bookservice {

Mode 1: Before, interface = Implementation class

Private Bookdao Bookdao = new Bookdaoimpl ();

Mode 2: interface + Setter

Private Bookdao Bookdao;

public void Setbookdao (Bookdao Bookdao) {

This.bookdao = Bookdao;

}

@Override

public void Addbook () {

This.bookDao.addBook ();

}

}

3.2 Configuration Files

<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 ">

<!--

Simulating the spring execution process

Create service instance: Bookservice bookservice = new Bookserviceimpl () IoC <bean>

To create a DAO instance: Bookdao Bookdao = new Bookdaoimpl () IoC

Set DAO to Service:bookService.setBookDao (Bookdao); DI <property>

<property> for attribute Injection

Name:bean property name, obtained by setter method

Setbookdao ##> Bookdao ##> Bookdao

Ref: reference to the ID value of another bean

-

<!--Create service--

<bean id= "Bookserviceid" class= "Com.itheima.b_di. Bookserviceimpl ">

<property name= "Bookdao" ref= "Bookdaoid" ></property>

</bean>

<!--creating a DAO instance--

<bean id= "bookdaoid" class= "Com.itheima.b_di. Bookdaoimpl "></bean>

</beans>

3.3 Testing

@Test

public void demo01 () {

Obtained from the spring container

String Xmlpath = "Com/itheima/b_di/beans.xml";

ApplicationContext ApplicationContext = new Classpathxmlapplicationcontext (Xmlpath);

Bookservice Bookservice = (bookservice) applicationcontext.getbean ("Bookserviceid");

Bookservice.addbook ();

}

Three minutes easy to understand Spring framework basics