10 recommended courses on mapping relationships

This article mainly introduces the basic class mapping and object relational mapping of Hibernate mapping in detail. It is of great practical value. Friends who need it can refer to it and recall some of the things we did when we didn’t learn ssh. When we created the database tables, first of all It is a database modeling E-R diagram, and then the relationship model is established through the entity model, and then the corresponding tables are established. There are three types of relationships between entities, one-to-one, one-to-many (or many-to-one), and many-to-many. Now, if we want to map the corresponding table based on the class, we can only map the database table through the relationship between classes and mapping files. We learn UML modeling. There are five relationships between classes, inheritance, implementation, association, dependency, aggregation/combination. The same is true for the relationship between entity classes in hibernate. We have implemented the code corresponding to different relationships. I am very familiar with it, so I am reviewing the knowledge about entity classes. The essence of Hibernate is Object Relational Mapping. ORM realizes saving object data into the database. In the past, we operated on the relational table and performed tasks such as addition, deletion, modification and query. Now we no longer perform

# on the relational table.

##1. Detailed explanation of examples of two types of Hibernate class mapping

Introduction: This This article mainly introduces the detailed explanation of basic class mapping and object relational mapping of Hibernate mapping. It is of great practical value. Friends who need it can refer to

2. java collection framework study notes

Introduction: Java collection class can be used to store multiple objects of varying numbers and can be implemented Commonly used data structures such as stacks, queues, etc. Unlike arrays, the length of arrays is immutable. Array elements can store basic types and object types, while collections can only store objects (essentially reference variables of objects). Java collections can be roughly divided into Set, List, and Map. Among them, Set represents an unordered, non-repeatable set, List represents an ordered, repeatable set, and Map represents a collection with a mapping relationship. The key in the map is unique and the value is repeatable. Its...

3. SQLAlchemy ORM example introduction to python

Introduction: ORM’s full name in English is object relational mapping, which is an object mapping relationship program. Simply put, for object-oriented programs like python, everything is an object, but the databases we use are all relational. In order to ensure consistent usage habits, the object model of the programming language and the relational model of the database are mapped through ORM, so that when we use the programming language to operate the database, we can directly use the object model of the programming language to operate. Instead of using sql language directly.

4. Interesting JavaScript question: Mapping of formal parameters and actual parameters

##Introduction: As an extension to the function function, you need to establish a correct mapping relationship between its formal parameters and actual parameters when a function is called. Let’s look at the following example first:

5.

Yii2.0 ArrayHelper::map() usage

Introduction: Construct a mapping (key-value form) from a multi-dimensional array or array. Specify the corresponding key value or value through the "$from" and "$to" parameters. Attribute name to set the mapping relationship. Of course, you can also further group mapping based on the grouping field "$group".

6.

Get the native data of the post request

Introduction: Sometimes, the data submitted by some requests is not the common parameter name: the key-value pair of the parameter value mapping relationship. For example, the data submitted by the WeChat public platform server to the developer's specified URL is xml characters. String...

7. java abstract classes and interfaces

Introduction: An important point in the object-oriented design process is how to abstract, that is, to establish an ideal one-to-one mapping relationship between the elements in the "problem space" and the elements in the "solution space". Abstract classes and interfaces are the products of the abstraction process.

8. The variables in PWP are “defined as you use them” function pwcorr txtpw pw public

Introduction: pw ,Variables: The variable "define as you use" function in PWP: The strict definition feature of variables in pascal is a good feature that can avoid errors and increase the maintainability of the code. But when used for web development, it seems verbose and difficult to handle, and not agile enough. If you use Variant to solve it, it will bring a performance loss in type conversion. The PWP engine has built-in mapping relationship support for some common data types. By using specially named variable names to directly infer its data type, it can be automatically applied in the program without defining it in advance. Respectively

9. php detects file types through file headers Common code classes (zip, rar, etc.

Introduction:: PHP detects file types through file headers. Common code classes (zip, rar, etc.: Sometimes we are not perfect in doing this. Some people may save some files, but By modifying the extension, it cannot be displayed during actual access (because the extension does not match the file content). The following PHP class may be able to help us. 1. PHP detection class. First of all, let me explain that the above mapping relationship between file headers and file types comes from the Internet. If you have a new file to check, you only need to add the mapping. If you need to know the file header information, you can use the tool: winhex to open the standard file search. For example: Code: Copy

10. Major discovery of Discuz DB layer cross-database mapping relationship table name prefix BUG, ​​discuz relationship table_PHP tutorial

##Introduction: Major discovery of the Discuz DB layer cross-database mapping relationship table name prefix BUG, ​​Discuz DB layer cross-database mapping. Relationship table name prefix BUG, ​​discuz relationship table scenario: Create a Table model in Discuz, but the library where the Table is located is not in the same library as Discuz. Discuz seems to be

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