Javaweb Learn 007-4 pages, 5 SQL statements (add, view, modify, delete) 2016-12-2

Need to review the Knowledge: Association query

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class module
Student Module
Course Modules
Hobby Module
User Information Module

The first thing a project has to do is write Tbuser, which corresponds to login.

Each module has a list page, add operation, view operation, modify operation, delete operation

DAO level is the level of database connection, it needs to write 6 Java method;
The biz level is the business logic judgment, which only needs to return the DAO result to the biz;
Web-level is the writing of each servlet;

For each module, the first is entity--and DAO--and Biz-->jsp and servlet authoring

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① for loop for each list page, configure Taglib with URI property and prefix property
②<c:foreach> must write 2 attributes
①items: Key key from the servlet must be written with an El expression for example: ${glist}
②var: Every time a loop is entered into the object
for (Grade g:list) {
Sysout (G.getgradeid ())
Sysout (G.getgradename ())
}

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Request.setattribute (' Rows ', rows) What's the use of this key?

Note: When you do non-null validation, the JavaScript statement is written in the child element of the head

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1.
Why view the page int stuid = Request.getparemeter
SELECT * FROM student where Stuid = 1
Because the view needs to be checked by the parameter ID, the page is passed to the servlet an ID value,
What about modifying the page?
Update student Set stuname = ' Where stuid= '
So modify the page not only need the ID value, also need to pass to a name value, to hide the primary key

But what's the use of hiding the primary key?

2.
<a href= "Dodetailstudent.action?stuid=${student.stuid}" > View </a>
<a href= "Toupdatestudent.action?stuid=${student.stuid}" > Modify </a>
<a href= "Dodeletestudent.action?stuid=${student.stuid}"
onclick= "return confirm (' Confirm Delete message? '); ' > Delete </a>

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3.
Students have to have classes in their tables.
Indicate which class the student is in, related query

Is-a is inherited
Has-a is a package

The writing of the Vo class:
is to query the students, to display the corresponding class name, that is, the associated query

4 pages, 5 SQL statements, 6 Java methods

Grade module (one side) Student Module (multi-party)
A class can have multiple students, which is the relationship established in the relational model diagram

Should be one of the primary keys of a party acting as a foreign key to many Parties
For example: Query student must be able to see grade information,
But query grade don't have to see student information
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In this case, the student module is the code of the many side of the writing and grade module is one of the party code writing
Difference:
Need to query to show the operation of the class: Queryall-detail.
Only the code for these two operations needs to be changed.

Public list<studentvo> queryallstudent ();
Public Studentvo detailstudent (int id);

is to replace the place where it was supposed to be student Studentvo
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But here's the problem:
Previously learned Database association, that is, the relationship model diagram drawing time, remember is not very clear.

How do I implement the grade and student associations?
Is it just when you're building a student table that you can write more than one column of grade's primary key?

Javaweb Learn 007-4 pages, 5 SQL statements (add, view, modify, delete) 2016-12-2