Guoxin Andong Camp Notes 2

02.15 am the next day

1. Start with IDEA development tools (IDE)

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1. Notes are very, very important!

 /**
 * Uncommented code is never called excellent
 */
 ​
 /**
 * Created with InteIIiJ IDEA.
 * User: thinklove
 */

1. The file description is also very important!

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1. IDEA starts

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   1. The first and second options create localized java projects, java web, etc.

   2. It is very important to choose the jdk version, not the latest, but the most stable version.

   3. It is better to use maven for package management.

   4. The difference between J2EE and Java EE: the old version is called J2EE, the new version will use Java EE 5 or higher, before 5 is called J2EE 1.4.

2. Type of server:

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    1. Jetty is more suitable for high-level personnel and supports dynamic configuration; tomcat supports fool-like configuration and is easier to use.

   1. WebLogic is charged, but it is easier to operate.

   2. WebSphere is from IBM.

   3. New Tomcat server:

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3. New Project

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      The JMX port represents the mapped port of the tomcat service. If you want one IDEA to open multiple tomacats, you need to configure the HTTP port and JMX port.

   3. The IDEA deployment method defaults to war package deployment.

   4. When running in IDEA, an out directory will be generated. Sometimes when there are too many modifications, the bug may not be updated in time, which will result in no modification after running. This is to delete the out directory and run it again.

   5. Enumeration has certain security risks.

4. The definition of the package name: domain name reversal. Example: www.qq.com package name is defined as com.qq. product name. development package name

5. Quick operation of IDEA:

   1. psvm quickly creates a standard main method

   2. sout quickly create input method

   3. Java creation project in IDEA is equal to C/S development; enterprise creation project is equal to B/S development.

 

2.15 pm

1. lib folder

   1. jackson is a new json format; mybatis is the database operation persistence layer; mybaties-Spring is the middle layer between mybaties and Spring.

   2. Put all jar packages under web/WEB-INF, then select all packages, right-click and select add as library..., put all packages into IDEA management; after all are under management, each jar package can be opened, That is, there is an arrow on the left; where META.INF is the configuration information; the other is the package file.

   3. For communication between different high-level languages, only text data format can be adopted, of which JSON is the most commonly used.

   4. Decompilation is a very important thing, you can look at other people's code structure.

2. Common mysql commands:

    show databases;
    //Display all schema (space) in the current database
    create database dlycrm20200215;
    //Create a table space, named after buy noodles
    use dlycrm20200215;
    //Use table space
    show tables;
    //View all tables in the current tablespace

3. The database password fields are currently stored in an encrypted and salted manner.

4. Introduction to SSM Framework:

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Among them, Spring + SpringMVC + Mybatis are very important, and you need to come down and study hard. The better plug-in now is Mybatis-Plus. But the mainstream of the enterprise is Mybatis.

The reflection in the framework is very important. The core content of JAVA must learn how to make a reflection state. After jdk5.0, it has become reflection + paradigm processing.

IOC: Inversion of Control (Inversion of Control, abbreviated as the IoC ), is an object-oriented programming one design principles can be used to reduce the computer code between the degree of coupling . The most common method is called dependency injection (Dependency Injection, referred to as DI ), there is a way called "dependent lookup" (Dependency Lookup). Through inversion of control, when an object is created, an external entity that regulates all objects in the system passes the reference of the object it depends on to it. It can also be said that the dependency is injected into the object.

1. The construction of the SSM framework (heavy and difficult points)

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   Filter is a filter, servlet-mapping is service configuration, and url-pattern is used to configure wildcards.