Shulou(Shulou.com)06/02 Report--

This article mainly talks about "what are the bean statements of Spring IOC". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn "what are the bean statements of Spring IOC?"

Introduction to Spring

Spring does not serve the development of web project functionality, or business. Instead, it serves the development of the project, facilitates the decoupling of each layer, facilitates the batch management of classes, and is a framework to improve the efficiency of software development and reduce the cost of maintenance in the later stage.

The core idea of Spring is IOC (inversion of Control) and AOP (faceted programming).

IOC: instead of requiring programmers to explicitly New an object, the Spring framework uses the objects created by the framework. Because they are created by the spring framework, the objects are saved in the spring framework object, also known as the spring container, so that spring knows which objects have been created in the current project, which layer the object belongs to, and how to manage it. The first thing you want to use the other features of spring is to use spring's objects, also known as handing control to spring management.

AOP: uniformly manage all classes under a certain path, or classes or methods with common characteristics, and add new functions before and after the execution of the original task. Make a series of unified accompanying actions such as monitoring, initialization, arrangement, destruction and so on.

If you've been working on Java programming for a while, you may find (and you may actually use it) that many frameworks tie applications to frameworks by forcing applications to inherit their classes or implement their interfaces. This intrusive programming approach can be seen in earlier versions of Struts and countless other Java specifications and frameworks. Spring strives to avoid messing up your application code with its own API. Spring does not force you to implement interfaces to the Spring specification or classes that inherit from the Spring specification. On the contrary, in applications built on Spring, its classes usually have no trace that you are using Spring. In the worst-case scenario, a class might use Spring annotations, but it is still POJO.

Any meaningful application (certainly more complex than the Hello World example) consists of two or more classes that collaborate with each other to complete specific business logic. Traditionally, each object is responsible for managing references to the objects it collaborates with (that is, the objects it depends on), which leads to highly coupled and difficult-to-test code.

IOC declares Bean

The Maven Poject is created first. The detailed package structure is as follows

Among them, AOP will explain in the next article.

Controller_.java

/ * *

* @ see HttpServlet#doGet (HttpServletRequest request, HttpServletResponse response)

* /

Protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

/ / TODO Auto-generated method stub

Response.getWriter () .append ("Served at:") .append (request.getContextPath ())

ClassPathXmlApplicationContext ctx=new ClassPathXmlApplicationContext ("/ ApplicationContext.xml")

Service_ s = (Service_) ctx.getBean ("service_Impl1_new")

System.out.println (s)

S.show ()

}

Since Spring cannot be demonstrated alone, Controller_.java creates a Servlet, directly calls the doPost or doGet method, implements Service, outputs the Service_ object s, and executes the show method.

Service_.java

Public interface Service_ {

Public void show ()

}

Create a Service interface to implement Spring.

1. No-parameter constructor declaration bean

Service_Impl1.java

Public class Service_Impl1 implements Service_ {

Public Service_Impl1 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service1- Parametric Construction method")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl1")

}

}

The output of the show method of rewriting Service_ implements Service_Impl1 and writes no-parameter construction methods.

ApplicationContext.xml

You only need to set the Service_Impl1,id corresponding to id and class,class is a parameter in the getBean called by Controller_.java. For the running result, please see the custom constructor injection bean.

two。 Custom constructor declaration bean

Service_Impl2.java

Public class Service_Impl2 implements Service_ {

Public Service_Impl2 (int a) {

/ / TODO Auto-generated constructor stub

System.out.println ("service2- Custom Construction parameters:" + a)

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl2")

}

}

ApplicationContext.xml

This is the parameter setting in the constructor. Index, as its name implies, means index, where a parameter is the 0th and value is the value of the parameter.

3. Single instance lazy loading declaration bean

Service_Impl3.java

Public class Service_Impl3 implements Service_ {

Public Service_Impl3 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service3- lazy load single instance")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl3")

}

}

ApplicationContext.xml

Lazy-init= "true" sets lazy loading, that is, bean is loaded only when called, not automatically; scope= "singleton" scope tag, that is, only one instance is created for a single instance.

4. Parameter reference declaration bean

Service_Impl4.java

Public class Service_Impl4 implements Service_ {

Service_ s3

Public Service_ getS3 () {

Return s3

}

Public void setS3 (Service_ S3) {

This.s3 = S3

}

Public Service_Impl4 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service4- parameter references bean")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl4")

}

}

ApplicationContext.xml

The parameter tag, name, is the bean to be referenced by the parameter s3jineref link in Service_Impl4.

5. Initialization property declaration bean

Service_Impl5.java

Public class Service_Impl5 implements Service_ {

String name

ArrayList list

HashMap map

HashSet set

@ Override

Public int hashCode () {

Final int prime = 31

Int result = 1

Result = prime * result + ((list = = null)? 0: list.hashCode ())

Result = prime * result + ((map = = null)? 0: map.hashCode ())

Result = prime * result + ((name = = null)? 0: name.hashCode ())

Result = prime * result + ((set = = null)? 0: set.hashCode ())

Return result

}

@ Override

Public boolean equals (Object obj) {

If (this = = obj)

Return true

If (obj = = null)

Return false

If (getClass ()! = obj.getClass ())

Return false

Service_Impl5 other = (Service_Impl5) obj

If (list = = null) {

If (other.list! = null)

Return false

} else if (! list.equals (other.list))

Return false

If (map = = null) {

If (other.map! = null)

Return false

} else if (! map.equals (other.map))

Return false

If (name = = null) {

If (other.name! = null)

Return false

} else if (! name.equals (other.name))

Return false

If (set = = null) {

If (other.set! = null)

Return false

} else if (! set.equals (other.set))

Return false

Return true

}

@ Override

Public String toString () {

Return "Service_Impl5 [name=" + name + ", list=" + list + ", map=" + map + ", set=" + set + "]"

}

Public String getName () {

Return name

}

Public void setName (String name) {

This.name = name

}

Public ArrayList getList () {

Return list

}

Public void setList (ArrayList list) {

This.list = list

}

Public HashMap getMap () {

Return map

}

Public void setMap (HashMap map) {

This.map = map

}

Public HashSet getSet () {

Return set

}

Public void setSet (HashSet set) {

This.set = set

}

Public Service_Impl5 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service5- initialization Properties")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl5")

}

}

The initialization parameters include list,map,set and normal parameters. The hashCode and equals methods are overridden. For more information, please see HashMap memory leak. The toString method is used to output initialization properties.

ApplicationContext.xml

QQQ

WWW

one hundred and eleven

Which gynecology hospital in Zhengzhou has a good http://www.sptdfk.com/

It is used in the map tag for assignment. Others normally use property and value for assignment.

6. The initialization property reference method returns the value declaration bean

Service_Impl6.java

Public class Service_Impl6 implements Service_ {

String s5_toString

Public String getS5_toString () {

Return s5_toString

}

Public void setS5_toString (String s5_toString) {

This.s5_toString = s5_toString

}

Public Service_Impl6 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service6- calling method return value")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl6 return value" + s5_toString)

}

}

The toString method of Service_Impl5 is called and output is made.

ApplicationContext.xml

Fixed is used to declare the return value of the calling method.

Reference the bean of the target

Method of referencing the target

7. Static factory-declare factory bean

Service_Impl7.java

Public class Service_Impl7 implements Service_ {

Public static Service_ StaticFactory (int num) {

Switch (num) {

Case 1:

Return new Service_Impl1 ()

Case 2:

Return new Service_Impl2 (100)

Case 3:

Return new Service_Impl3 ()

Case 4:

Return new Service_Impl4 ()

Case 5:

Return new Service_Impl5 ()

Default:

Return new Service_Impl6 ()

}

}

Public Service_Impl7 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service7- static factory")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl7")

}

}

The static factory uses the switch statement in the implementation class to simulate, and the static factory adds the static keyword before the method to call the other implementation class methods above.

ApplicationContext.xml

Use constructor injection methods to assign values; factory-method= "StaticFactory" (method name of the factory-method factory)

8. Instance factory-declaration factory bean

Service_Impl8.java

Public class Service_Impl8 implements Service_ {

Public Service_ factory1 (int num) {

Switch (num) {

Case 1:

Return new Service_Impl1 ()

Case 2:

Return new Service_Impl2 (100)

Case 3:

Return new Service_Impl3 ()

Case 4:

Return new Service_Impl4 ()

Case 5:

Return new Service_Impl5 ()

Default:

Return new Service_Impl6 ()

}

}

Public Service_Impl8 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service8- instance Factory")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl8")

}

}

ApplicationContext.xml

To create an instance factory bean, first create an instance factory's bean, and then create a factory method's bean to call the factory's bean.

To call the bean of the factory method when calling, call service_Impl8_new here

9. Comment declaration bean

@ Service: used to annotate business layer components

@ Controller: used to annotate control layer components (such as action in struts)

Repository: used to annotate the data access component, that is, the DAO component

@ Component (value= "*"): generally refers to components. We can use this annotation to annotate components when they are not easy to classify.

Service_Impl9.java

@ Service

Public class Service_Impl9 implements Service_ {

Public Service_Impl9 () {

/ / TODO Auto-generated constructor stub

System.out.println ("service9- comments are injected into bean")

}

@ Override

Public void show () {

/ / TODO Auto-generated method stub

System.out.println ("Service_Impl9")

}

}

@ Service declares bean (comments can only declare no-parameter constructors. Bean declared by default with annotations is lowercase of the class name. The id of the declared bean here should be service_Impl9.

ApplicationContext.xml

Annotations need to be scanned with annotations, where base-package is the directory scanned, and the root directory of the project is generally used. if you use SpringMVC later, you don't have to scan Controller.

Comments are written to bean

@ Resource (name= "" type= "") bean write

@ Autowired/@Qualifier

@ inject/@named

At this point, I believe you have a deeper understanding of "what are the bean statements of Spring IOC?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.