Summary of database 2

1.JDBC

Use of transmitter PreparedStatement Preprocessing statement , Can prevent sql Inject , Its preprogrammed performance is high . Security , Efficient ,sql concise

Statement: The parent interface ,sql Manual splicing parameters are required .

2.Maven

• development tool ： The front end uses HBuilderX, The back end uses eclipse/idea
• project management ： The front end uses npm、webpack, The back end uses Maven、SpringBoot
• web middleware ： The front end uses NodeJS, The back end uses Tomcat

maven: download , management , compile jar package

A classic business request process ：

front end html Page launch ajax request （http://localhost:8080/factoryController/findAll）, visit SpringMVC Framework of the Controller Control layer ,SpringMVC Framework resolution request , Find one to call Controller, Find one findAll Method , At the same time, the parameters submitted by the request are encapsulated in java In the object . after Controller The layer passes the request to Spring Framework of the Service The business layer ,Service The layer is passing the request to Mybatis Framework of the Mapper Persistence layer ,Mapper visit MySQL Database queries database tables , The query result is returned to Mapper layer ,Mapper Return to Service layer ,Service Return to Controller layer .Controller hold java Data to json character string , Return to ajax call ,ajax Make a callback and put json String conversion to js object , In the page, you can pass js/vue analysis js object , Finally, show the data to html On the page .

Four characteristics :

1.reposity: Local repository , Create your own folder , For storage maven Download it from the image jar package

2. coordinate :

        coordirate, For storing and searching jar The location of the package

        groupId: Usually the company's domain name

        artifactid: project id, Usually the name of the project

3. rely on : You can specify what you want <dependeneies/> Download the image warehouse to the local warehouse .

4. command : Common commands :

• clean Clean cache
• package pack jar、war
• install install jar To the local warehouse

3.IDEA plug-in unit

1.lombok:@Data： Act on a class , Is a collection of the following annotations ：@ToString @EqualsAndHashCode @Getter @Setter @RequiredArgsConstructor

2.SpringBoot Thermal deployment : Changed the code , You don't have to restart , Just recompile to access the new data .SpringBoot The core mechanism : " Open the box " Just import specific jar Package file You can use the functions directly The root cause : SpringBoot It's a simplification of the framework , It's expanded internally , No programmer required .

4.json

JSON refer to JavaScript Object notation , A lightweight data exchange format

Send data to the server : take JS Conversion of objects JSON character string JSON.stringify(Js object )

Accept data from the server : JSON String to JS object JSON.parse("json character string ")

5. Database optimization

1. Use the field name in select Instead of *

2.where Use in and Instead of or

3. Use as much as possible varchar Instead of char, Use numbers instead of string types

4. The return value of the query should not be large

5. Build indexes to improve query efficiency

6.where Try not to use <> or != The operator

7. Optimize like sentence : Fuzzy queries are best started with certain characters

8. Batch insertion performance improvement

9. duplicate removal distinct Filter fewer fields

6.vue

1.vue Of ajax: Asynchronous access , Partial refresh

2.axios The request header Content-Type The default is application/json, and postman The default is application/x-www-form-urlencoded.

ajax/postman It is generally used @RequestParam Receiving parameters ：

axiso use @RequestBody Of json Mode to receive parameters :@RequestBody, Will the incoming json Convert string to Json object

3.Vue Why is this called a framework : Applied to Observer mode : The observer pattern defines a one to many dependency , Let multiple observer objects listen to a target object at the same time , When the state of the target object changes , All observer objects will be notified , Enable them to update automatically .