[UML] UML class diagram

The installation steps are ：File -> Settings -> Plugins Search for PlantUML , find PlantUML integration And install .

1.UML Basic introduction

1) UML——Unified modeling language UML ( Unified modeling language ), It is a language tool for software system analysis and design , It is used to help software developers think and record the results of ideas

2) UML It is a set of rules of symbols , Just like mathematical symbols and chemical symbols , These symbols are used to describe the various elements in the software model and their relationships , Such as class 、 Interface 、 Realization 、 generalization 、 rely on 、 Combine 、 Polymerization, etc. , Like the picture on the right :

 

2.UML chart

draw UML The picture is similar to writing an article , They describe their thoughts to others , The key is thinking and organization ,UML Picture classification ：

1) Use case diagram (use case)

2) Static structure diagram ： Class diagram 、 Object graph 、 Package diagram 、 Component diagram 、 Deployment diagram

3) Dynamic behavior diagram ： Interaction diagram （ Sequence diagram and collaboration diagram ）、 State diagram 、 Activity diagrams

3.UML Class diagram

1) Used to describe classes in the system ( object ) Its composition and class ( object ) All kinds of static relations between .

2) Relationships between classes ： rely on 、 generalization （ Inherit ）、 Realization 、 relation 、 Aggregation and combination .

3) attribute / The plus and minus signs preceding the method name represent this property / Visibility of methods ,UML There are three symbols for visibility in class diagrams ：

+： Express public

-： Express private

#： Express protected

The complete representation of attributes is ： visibility name ： type [ = The default value ]

The complete representation of a method is ： visibility name ( parameter list ) [ ： Return type ]

4 . Class diagram — Dependence （Dependence）

As long as the other party is used in the class , Then there is a dependency between them . If there's no one else , I can't even pass the compilation .

 public class PersonServiceBean {
 private PersonDao personDao;// class 
 public void save(Person person){}
 public IDCard getIDCard(Integer personid){}
 public void modify(){
 Department department = new Department();
 }
 }
 public class PersonDao{}
 public class IDCard{}
 public class Person{}
 public class Department{}

Class diagram ： rely on

 

Summary :

1) Class uses the other side

2) If it's a member property of a class

3) If it's the return type of the method

4) Is the type of parameter the method receives

5) Method used in

5. Class diagram — Generalization off (generalization）

Generalization is actually inheritance , He's a special case of dependency

 public abstract class DaoSupport{
 public void save(Object entity){
 }
 public void delete(Object id){
 }
 }
 public class PersonServiceBean extends Daosupport{
 }

Class diagram ： Inherit

 

Summary :

1) Generalization is actually inheritance

2) If A Class inherited B class , We said A and B There is a generalization relationship

6. Class diagram — Realization relationship (Implementation)

Realizing a relationship is actually A Class implementation B Interface , He's a special case of dependency

 public interface PersonService {
 public void delete(Interger id);
 }
 public class PersonServiceBean implements PersonService {
 public void delete(Interger id){}
 }

Class diagram ： Realization

 

Summary ：

7. Class diagram -- Connections （Association）

Association is actually the relationship between classes , It is a special case of dependency

The association is navigable ： That is, two-way association or single Association .

Relationships are multiple ： Such as "1"（ It means that there is only one ）,"0..."（ Express 0 One or more ）,"0,1"（ Express 0 One or one ）,“n,m”( Express n To m Every one can ),“m...*”（ At least m individual ）.

 // Single one-to-one relationship 
 public class Person{
 private IDCard card;
 }
 ​
 public class IDCard{}
 ​
 // Two way one-on-one relationship 
 public class Person{
 private IDCard card;
 }
 public class IDCard{
 private Person person;
 }
 ​
 // Many to many relationship 

Class diagram ： relation

 

Summary ：

The type of the attribute of the associated class

8. Class diagram — Aggregate relationship （Aggregation）

Aggregate relationship （Aggregation） It means the relationship between the whole and the part , The whole and the part can be separated . Aggregation is a special case of association , So it's associated with navigation and multiplicity .

Such as ： A computer consists of a keyboard (keyboard)、 Monitor (monitor), Mouse, etc ; The components of a computer can be separated from the computer , Use a solid line with a hollow diamond to represent .

 public class Computer{
 private Mouse mouse;
 private Monitor monitor;
 ​
 public void setMouse(Mouse mouse){
 this.mouse = mouse;
 }
 public void setMonitor(Monitor monitor){
 this.monitor = monitor;
 }
 }

Class diagram ： polymerization

 

Summary ：

Aggregate relationship （Aggregation） It means the relationship between the whole and the part , The whole and the part can be separated .

9. Class diagram — synthetic relation （Composition）

synthetic relation ： It's also the relationship between the whole and the part , But the whole cannot be separated from the part .

Let's look at another case ： In the program we define the entity ：Person And IDCard、Head, that Head and Person Namely Combine ,IDCard and Person It's polymerization .

But if in the process Person The entity defines right IDCard Cascade delete , Delete immediately Person Together with IDCard Delete... Together , that Well IDCard and Person It's a combination .

 public class Person{
 private IDCard card;
 private Head head = new Head();
 }
 public class IDCard{}
 public class Head{}

Class diagram ： Combinatorial aggregation

 public class Computer {
 private Mouse mouse = new Mouse(); // Mouse can and  computer  Can't separate 
 private Moniter moniter = new Moniter();// The monitor can be connected with  Computer  Can't separate 
 public void setMouse(Mouse mouse) {
 this.mouse = mouse;
 }
 public void setMoniter(Moniter moniter) {
 this.moniter = moniter;
 }
 }
 public class Mouse {
 }
 public class Moniter {
 }

Class diagram ： Combine

 

Summary ：

When the composite reference class is instantiated , The referenced class is also instantiated