Spring (Read external database configuration information, annotation-based management bean, DI)

# # # parsing external configuration file
Under the Resources folder, create a new db.properties (and database connection related information)

Driverclassname=com.mysql.jdbc.driver
url=jdbc:mysql://localhost:3306/db
Username=root
Password=root

Development steps
1) Create a MAVEN project
Add Web. xml
Add Tomcat Runtime Environment
Add Jar Spring-webmvc,junit,commons-dbcp,mysql
Add Application.xml
2) connection pooling information for the configuration database

 <!--1.util:properties represents reading an external property file and instantiating the object 2.id representing the name 3.location representing the location of the property file <util:properties id= "dbconf" location= " Classpath:db.properties > < connection pooling for!--configuration database 1. Use spring expressions to assign a value to an attribute 2.spring expression syntax format: #{}- -<BeanID= "DataSource"class= "Org.apache.commons.dbcp.BasicDataSource"><BeanID= "DataSource"class= "Org.apache.commons.dbcp.BasicDataSource">     < Propertyname= "Driverclassname"value= "#{dbconf.driverclassname}"/>     < Propertyname= "url"value= "#{dbconf.url}"/>     < Propertyname= "username"value= "#{dbconf.username}"/>     < Propertyname= "Password"value= "#{dbconf.password}"/> </bean>

# #基于注解的bean管理
# 1. Instantiating an object based on annotations (recommended)
    instantiating objects and dependency injection in two ways: Configuration file, annotations

1. Scan package   (profile)
<!- -Scan package can scan all class--> under current package and sub-package;
     <context:component-scan  base-package= "Cn.tedu.dao" >

2. Annotations for specific functions ( instantiation function)
      @Component general annotations: instantiating objects
      @ Controller: Instantiating objects of the control layer class
      @Service: Instantiating objects of the business layer class
      @Reponsitory: Instantiating objects of the persistence layer class

@Repository ("Userdao")      publicclassimplements  userdao{             publicvoid  Insertuser () {                 System.out.println ("added successfully! ");        }

In MyBatis, it is generally defined an interface in which an abstract method is defined and the corresponding abstract method is implemented in the configuration file.

#2. Life Cycle Management

//@Component represents an instantiated object@Component Public classBeanlife { PublicBeanlife () {System.out.println ("Beanlife");}//@PostConstruct represents a method of defining initialization//@PostConstruct: Tomcat run environment-dependent jar package@PostConstruct Public voidinit () {System.out.println ("Init");} Public voidExecute () {System.out.println ("Execute");}//@PreDestroy represents a method for defining destruction//@PreDestroy: Tomcat run environment-dependent jar package@PreDestroy Public voiddestroy () {System.out.println ("Destroy");}}

# #3. Bean scope

// instantiate an object with annotations, default to Singleton Singleton // @Scope Define the scope of the bean // @Scope ("prototype") indicates that the bean scope is a multi-instance @Component @scope ("prototype")  Public class Demoscope {}

# #4. Lazy Loading

Instantiation of the default Bean object, which is immediately loaded
@Lazy to set whether the bean deferred loading annotations
@Lazy (True) to set the Bean object for lazy loading

@Component @lazy (true)  Public class Demolazy { public demolazy () {System.out.println ("Demolazy");}}

#DI (dynamically provide the object it wants to an object)

Reference: http://www.360doc.com/content/18/0125/09/27831725_724899826.shtml
##[email protected] (recommended)

[email protected] The Tomcat runtime environment relies on annotations defined in the JAR package
[Email protected] implementing Dependency Injection
[email protected] to implement dependency injection, you can omit the Set method
[email protected] The default dependency injection method is ByName
[Email protected] If there are no matching attributes
Implement dependency injection in bytype manner
[Email protected] (name= "Userdaoimpl")

  @Resource (name= "Userdaoimpl")     private Userdao Userdao;

##[email protected] (Learn)

public class USERSERVICEIMPL2 implements userservice2{
[Email protected] Dependency Injection
[Email protected] Default Dependency injection method Bytype;
If there are multiple objects of the same type, then follow the byname dependency injection
3. If you use ByName to implement dependency injection,
Use @qualifier annotations to define matching names
[email protected] cannot be used alone

@Autowired @qualifier ("Userdaoimpl") Private Userdao Userdao;  Public void AddUser () {Userdao.insertuser ();}}

##[email protected] (Learn)

@Component  Public class Student {//@Value ("Admin") to string or base data type Dependency Injection //@Value ("#{conf.name}") Use the spring expression to implement a dependency injection @Value ("#{conf.name}")private  String name;  Public String toString () {return ' name= ' +name;}}

Spring (Read external database configuration information, annotation-based management bean, DI)