SSM assembly

brief introduction

SSM The assembly is Spring + SpringMVC + MyBatis Integration of the framework , Divide the system into view layers 、 Control layer 、 Service layer 、 The data layer .

controller The controller will be used service service ;service The service will be used mapper Data mapping and converting data into domain Data objects ;mapper Data mapping will be used domain Define data types .

entity： Data objects , It can reduce the data processing process .

model： stay entity On the basis of improvement , Make the data more humanized .

domain： stay model Expand and integrate data sources based on , It can enrich data and diversify .

Controller registration

adopt @Controller and @RestController Annotations can automatically register the controller into the project , Pass again like this @RequestMapping Annotations can map requests , Generally, you can access pages or data .

By the way @RestController = @Controller + @ResponseBody, Its source code is basically the same .

The controller is scanned

When class is used @Controller To register the controller and be able to Spring Application scanning can be divided into two cases ：

1. External dependencies are referenced into the project

   You can probably understand that when the controller is not in the current project , But in the dependency package of the project , for example SpringSecurity Default login page , It is referenced through external modules .

2. And Spring Application startup class peer automatic scanning

spring-boot-starter-web

file ：https://www.yiibai.com/spring-boot/spring-boot-starter-web.html

spring-boot-starter-web The integration package includes web、webmvc and tomcat .

therefore tomcat The server and Spring MVC The framework is automatically configured , Greatly reduce the amount of development .

If you want to configure the server yourself , Can also be spring-boot-starter-tomcat Exclude items from use tomcat The server .

mybatis-spring-boot-starter

file ：http://www.mybatis.cn/archives/861.html

mybatis-spring-boot-starter Integration package is right MyBatis + MyBatis-Spring + SpringBoot Integrated packaging of , Therefore, it is highly dependent , But it greatly reduces the amount of development , You don't have to configure SqlSessionFactory And transaction processing .

function

• Automatically discover existing data sources

• utilize SqlSessionFactoryBean Create and register SqlSessionFactory

• Create and register SqlSessionTemplate

• Automatic scanning Mapper, And register to the Spring Context environment facilitates the injection and use of programs

  By default, it will find @Mapper Annotation marker mapper , In addition, you can actually pass @MapperScan Annotations to scan packages .

MyBatis

MyBatis Is an excellent persistence layer framework , It supports customization SQL、 Stored procedures and high-level mappings .MyBatis It dispenses with almost everything JDBC Code and the work of setting parameters and getting result sets .MyBatis It can be done by simple XML Or annotations to configure and map primitive types 、 Interface and Java POJO（Plain Old Java Objects, Ordinary old-fashioned Java object ） For records in the database .

SqlSession

file ：https://mybatis.net.cn/java-api.html#sqlSessions

SqlSessions By SqlSessionFactory Instance created .SqlSessionFactory Object contains create SqlSession Examples of various methods . and SqlSessionFactory Itself is made up of SqlSessionFactoryBuilder Created , It can come from XML、 Note or Java Configure code to create SqlSessionFactory.

XML mapper

file ：https://mybatis.net.cn/sqlmap-xml.html

The element tag

label	describe
cache	Cache configuration of namespace
cache-ref	Cache configuration referring to other namespace
resultMap	Describes how to load objects from a database result set
sql	sql sentence , A block of repeatable terms that can be referenced by other statements
insert	Mapping insert statements
update	Mapping update statements
delete	Mapping delete statements
select	Mapping query statements

Element attributes

attribute	value	The default value is	scene	describe
id	string	——	[select	update
parameterType	object	unset	[select	update
resultType	object	——	[select	update
resultMap	object	——	[select	update
flushCache	boolean	false	[select	update
useCache	boolean	true	select	If this statement is called, the result will be cached by the L2 cache .
timeout	int	unset	[select	update
fetchSize	int	unset	[select	update
resultOrdered	boolean	false	[select]	If true, It is assumed that nested result sets or groups are included , When a main result row is returned , There is no reference to the previous result set . This makes it possible to get nested result sets without running out of memory .
resultSets	[object…]	——	[select]	This setting only applies to multiple result sets . It will list the result sets returned after the statement is executed and give each result set a name , Multiple names are separated by commas .
useGeneratedKeys	boolean	false	[insert	update]
keyProperty	string	unset	[insert	update]
keyColumn	string	——	[insert	update]

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