review

EL

1. Syntax ${expression}
2. EL domain objects, and lookup rules
   • pageScope
   • requestScope
   • sessionScope
   • applicationScope
3. What is the function of pageContext object in EL
   • You can get other objects
   • ${ pageContext.request.contextPath }
4. How does EL display the attributes of students, elements in list and elements in map
   • ${Student object. Property name}
   • ${list [index]}
   • ${map.key} or ${map["key"]}
     • name-abc
     • 1
5. empty operator in EL
   • Judge whether the variable is null
   • String ''
   • The collection has no elements

JSTL

1. <%@ taglib uri=".../jsp/jstl/core" prefix="c" %>

2. Conditional judgment label

   <c:if test="${condition}"></c:if>
   

3. Circular label

   <c:forEach items="${ Collection or array }" var="Temporary variable name corresponding to each element">
   	${Temporary variable name}
   </c:forEach>
   

mvc concept

• Model model (data), such as student
• View view (display data), such as jsp
• controller controllers (linking models and views) such as servlet s
• How do they combine

filter

1. Define and configure filters

   @WebFilter("/Filtered resource path")
   public class Filter class implements Filter {
       
       public void doFilter(request, response, FilterChain chain) {
           // Release
           chain.doFilter(request, response);
       }
       
   }
   

2. How to release requests and how to intercept requests

3. Interception order of multiple filters

   • Sort by the class name of the filter, and filter from small to large (annotation method)

Today's content

1. Filter xml configuration (*)

<filter>
	<filter-name>name</filter-name>
    <filter-class>Full path of class</filter-class>
    <init-param>
    	<param-name>Initialization parameter name</param-name>
        <param-value>Initialization parameter value</param-value>
    </init-param>
</filter>

<filter-mapping>
    <filter-name>name</filter-name>
    <url-pattern>/Filter resource paths</url-pattern>
</filter-mapping>

• The order of filter execution in xml mode is the order of filter mapping (*)

• FilterConfig.getInitParameter("initialization parameter name") returns the initialization parameter value

2. Filter interception position (understand)

• request
• forward
• include
• error
• async

<error-page>
    <exception-type>Exception type</exception-type>
    <location>/Error page</location>
</error-page>

<error-page>
    <error-code>Error status code (404),500)</error-code>
    <location>/Error page</location>
</error-page>

3. Classification of listeners (understand)

Events (application start, application stop, request object creation, session object creation, and session object destruction)

• ServletContextListener(*)

  @WebListener
  public class Listener class implements ServletContextListener{
      public void contextInitialized(ServletContextEvent event) {
          // event gets the ServletContext object just created
          event.getServletContext();
      }
      public void contextDestroyed(ServletContextEvent event) {
          // event gets the ServletContext object to be destroyed
      }
  }
  

  Together, the three components of the web (servlet, filter and listener) can also configure listeners in xml:

  <listener>
      <listener-class>Listener class full path</listener-class>
  </listener>
  

• HttpSessionListener

• ServletRequestListener

• ServletContextAttributeListener

• HttpSessionAttributeListener

• ServletRequestAttributeListener

  • When setAttribute and removeAttribute are called, the corresponding events of the above listeners will be triggered

• HttpSessionBindingListener

// Student stu = new Student()
// session.setAttribute("student", stu);
// session.removeAttribute("student");
public class Student implements HttpSessionBindingListener {

    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        // Execute when this object is put into the session domain
    }

    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
        // Execute when this object is removed from the session domain
    }
}

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If an object like Student is to be stored in a session, it must implement the Serializable interface, otherwise it cannot be used with the passivation and activation functions (understand)

mysql

sql structured query language

• oracle
• mysql
• sql server

1. Introduction and installation

mysql client software

• sqlyog
• navicat

Database database

table

Row record line

Column column

Data data

dba database administrator

2. SQL statement

ddl - create, modify and delete library tables

create database [if not exists] Library name [character set character set];

alter database Library name character set New character set

drop database [if exists] Library name;

show databases;  -- View all library tables

show create database Library name; -- View a database creation statement

use Library name;

View the character set of the table

show create table user \G

Table data type (*)

Int - a 4-byte integer

Tinyint - 1 byte

Smallint - 2 bytes - short

bigint - 8 bytes - long

Varchar (maximum length) - string. For example, varchar(10) means that it can store up to 10 characters

The datetime range is large

timestamp is not recommended. The scope is small

a key

create table Table name (
	Column 1 type [constraint],
    Column 2 type [constraint],
    ...
	column n type [constraint]
) [character set character set];

Understand (all can be completed through the graphical interface)

alter table Table name rename to New table name;  -- Modify table name
alter table Table name add New column name type [constraint];  -- Add column
alter table Table name modify New type of column name [New constraint];  -- Modify column
alter table Table name drop Listing;  -- Delete column
alter table Table name change Old column name new column name new type [New constraint];  -- Modify column

desc Table name; -- See which columns are in the table

drop table [if exists] Table name; 

show tables; -- See which tables are available

show create table Table name; -- View table creation statements (including character sets)

dml - add, delete and modify data (*)

dql - query data (*)

dcl - rights management

3. Constraints

Divide column name new type [new constraint]; – Mo dify column
alter table name drop column name; – Delete column
alter table name change old column name new column name new type [new constraint]; – Modify column

desc table name; – See which columns are in the table

drop table [if exists] table name;

show tables; – See which tables are available

show create table name; – View table creation statements (including character sets)

#### dml - add, delete and modify data (*)

#### dql - query data (*)

#### dcl - rights management



### 3. Constraints