Senior short-term training 0831 (ssm)

0831 summary

The first is talked about some of the basic foundation of Java, then that is their practical realization of a collection from the class definition, in this collection classes, like the realization of the same list, there is the initial length (size), when the length is more than a collection of the initial length of the collection class, to be expanded length (e.g. ArrayList expansion is expanded to 1.5 times, Vector is expanded to 2 times the original), must add function, GET functions are actually implemented interfaces ;

package peixun;

import java.util.Collection;

import java.util.Iterator;

java.util.Spliterator import;

import java.util.Spliterators;

public interface settest<E> extends Collection<E> {

int size();

boolean isEmpty();

boolean contains(Object o);

Iterator<E> iterator();

<T> T[] toArray(T[] a);

boolean add(E e);

boolean remove(Object o);

boolean containsAll(Collection<?> c);

boolean addAll(Collection<? extends E> c);

boolean retainAll(Collection<?> c);

boolean removeAll(Collection<?> c);

void clear();

boolean equals(Object o);

int hashCode();

@Override

default Spliterator<E> spliterator() {

return Spliterators.spliterator(this, Spliterator.DISTINCT);

}

Then explain that a bit of the current framework technology (companies with more is SpringBoot, SSH, SSM) personal understanding, or SpringBoot better use some, but can not say that it will only use their own feel good, the rest will not, so even if he will be very front-end technology, but the technology used and the company's main inconsistency, inevitably there will be problems at work, so, for our students, we have to grasp a lot, as long as it can with something, we have to learn, here, to make a personal collate and summarize the framework for SSM:

SSM is the combination SpringMVC, Spring and Mybatis of.

SpringMVC: It is used for the web layer corresponds Controller (equivalent to the conventional and the struts servlet Action), to process the user request. Before learned SpringBoot which is then analyzed by the controller of the user's request and returns a string (the string is usually the name of the page you want to return, because the prefixes and suffixes in our framework have been defined, of course, himself can be modified custom) in the configuration file, then the string will lead us to the page you want us to go back to one of our designated.

E.g:

@Controller

@RequestMapping("/book")

public class BookController {

private Logger logger = LoggerFactory.getLogger(this.getClass());

@Autowired

private BookService bookService;

@RequestMapping(value = "/list", method = RequestMethod.GET)

private String list(Model model) {

List<Book> list = bookService.getList();

model.addAttribute("list", list);

// list.jsp + model = ModelAndView

return "list";// WEB-INF/jsp/"list".jsp

}

Here, in fact, we have by sending a request (this request is that list, that is, our visit is the local host address bar: // 8080 / list), then the request will be through our program, our Controller it is resolved, and there may be a series of operations related function or operation and so on, then you can return a string type of string that is what we want to address our visit, of course, prefixes and suffixes splicing when necessary, so as to access to the page we want to go,

Spring: too strong, so I can not use a word or phrase to summarize it. But we usually estimate the development of the contact is the most IOC containers, which can be loaded bean (that is, we java in the class, of course, including service dao inside), with this mechanism, we do not use this in every class when it is initialized, rarely see the keyword new. The additional spring aop, transaction management, and so are we often use.

MyBatis: personally feel better with MyBatis compared to Hibernate. First, it can be freely controlled sql, the code which will have a database prepared by experienced people can do to enhance the efficiency of database access. Second, it can use the xml way to manage our organization sql, because the general procedural error in many cases sql error, others took over after the code can quickly find wrong place, or even the original can be optimized write sql. Since the first systematic study of the individual is SpringBoot, SpringBoot is generally the integration of these, inside the framework of these mechanisms, in SpringBoot in both, MyBatis for my personal understanding is a series of operations on the database, then we do not like as the beginning of each operation must be written to the database related methods, so that when the project is running, will be more tired, because this should also be developed on MyBatis, find the problem is more convenient, but also simple.

For example: In our dao which has such a function code:

Appointment queryByKeyWithBook(@Param("bookId") long bookId, @Param("studentId") long studentId);

In it is the name of the function queryByKeyWithBook, and has passed the relevant parameters in the back, is a is a bookid syudentid, then it will be implementation-dependent in our method of operating a mapper in:

<! - tell MyBatis how to map the results to a map book while Appointment Properties ->

<! - free to control SQL ->

SELECT

a.book_id,

a.student_id,

a.appoint_time,

b.book_id "book.book_id",

b.`name` "book.name",

b.number "book.number"

FROM

appointment a

INNER JOIN book b ON a.book_id = b.book_id

WHERE

a.book_id = #{bookId}

AND a.student_id = #{studentId}

</select>

This is called our operating methods, and then we will return value to Appointment types return, of course, Appointment is our entity class a.

Second, our framework is no longer used jdbc 'way connected to a database, and now we have the link to the database is basically all done in the configuration file;

Ssm e.g. jdbc.properties herein in:

jdbc.driver=com.mysql.jdbc.Driver

jdbc.url=jdbc:mysql://localhost:3306/340message?useUnicode=true&characterEncoding=utf8

jdbc.username=root

jdbc.password=root

There are links to the database in SpringBoot is also full realization in the database:

spring:
datasource:
    username: root
    password: root
    url: jdbc:mysql://192.168.2.108:3306/mybatis
    driver-class-name: com.mysql.cj.jdbc.Driver

Again summarize the main level of the architecture ssm:

For our directory levels:

Dao is the data access layer (interfaces) to deal with data, can be database operations, file read and write operations can be even redis cache operation, in short, all the data related to the operation on here, it was also called the dal or data persistence layer almost all meaning. We use the mybatis, so each interface method can be implemented directly in the configuration file.

Entity is the entity class, the general database corresponding to the appearances, dao encapsulating layer is taken out of a data object is, we often say POJO, generally only between dao transfer layer and the service layer.

Dto is the data transport layer, and a lot of time an entity can not meet our business needs, the information may be presented to the user very much, this time there will be a dto, also equivalent to vo, do not mix in this entity inside

Service is the business logic (interfaces), there is to write our business logic, it was also called bll, in the design of service interfaces should stand when the "user" perspective.

serviceImpl is the business logic (realized), to achieve our business interface, control GS is written here.

Web is the controller, springmvc is here to play a role, also called controller controller, the equivalent of struts in action.

In mapper in grammatical structure is:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<- Objective:! To dao provide interface methods sql statement Configuration ->

<-! Specific SQL ->

SELECT

book_id,

name,

number

FROM

book

WHERE

book_id = #{bookId}

</select>

SELECT

book_id,

name,

number

FROM

book

ORDER BY

book_id

LIMIT #{offset}, #{limit}

</select>

UPDATE book

SET number = number - 1

WHERE

book_id = #{bookId}

AND number > 0

</update>

</mapper>

Project is a maven, so pom.xml is essential:

<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/maven-v4_0_0.xsd">

<groupId>com.soecode.ssm</groupId>

<version>0.0.1-SNAPSHOT</version>

<name>ssm Maven Webapp</name>

<url>http://github.com/liyifeng1994/ssm</url>

<! - Test Unit ->

<groupId>junit</groupId>

<artifactId>junit</artifactId>

</dependency>

<! - 1. Logs ->

<-! Slf4j implement the interface and integration ->

<groupId>ch.qos.logback</groupId>

<artifactId>logback-classic</artifactId>

</dependency>

<! - 2. Database ->

<groupId>mysql</groupId>

<artifactId>mysql-connector-java</artifactId>

<scope>runtime</scope>

</dependency>

</dependency>

<! - DAO: MyBatis ->

<groupId>org.mybatis</groupId>

<artifactId>mybatis</artifactId>

</dependency>

<groupId>org.mybatis</groupId>

<artifactId>mybatis-spring</artifactId>

</dependency>

<groupId>taglibs</groupId>

<artifactId>standard</artifactId>

</dependency>

</dependency>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

</dependency>

<groupId>javax.servlet</groupId>

<artifactId>javax.servlet-api</artifactId>

</dependency>

<-! 1) Spring Core ->

<groupId>org.springframework</groupId>

<artifactId>spring-core</artifactId>