Spring Config Bean

　A Bean is a class

　　　　The code is parsed on the basis of the spring IOC and DI implementation case

　　How the Bean is instantiated:

1. Non-parametric construction

<bean id= "UserService" class= "com.baidu.test.UserServiceImp" >        <property name= "name" value= "Zhang San" > </property>        </bean>

2. Static Factory method

Applicationcontext.xml

class= "Com.baidu.test.BeanFactory2" factory-method= "Createuserserviceimp" >              <property name= "name" value= "Zhang San" ></property>        </bean>

Creating the BeanFactory2 Class

public class BeanFactory2 {public static UserService Createuserserviceimp () {return new Userserviceimp ();}}

3. Instance Factory method

<bean name= "BeanFactory2" class= "Com.baidu.test.BeanFactory2" ></bean>       <bean id= "UserService" Factory-bean= "BeanFactory2" factory-method= "Createuserserviceimp" >        <property name= "name" value= "Zhang San" > </property>       </bean>

Creating the BeanFactory2 Class

public class BeanFactory2 {public  userservice Createuserserviceimp () {return new Userserviceimp ();}}

　　　　Scope of the Bean

There is a scope in the Bean's properties to describe the scope of the bean.

Singleton	Singleton spring IOC container with only one Bean real class (default scope)
Prototype	A new instance is returned when multiple cases are fetched from the spring container
Request	Store the Bean Object Request.setattribute () in the request domain
Session	Store the Bean Object Session.setattribute () in the Session field

Common Singleton and prototype in development (singleton and multiple cases)

Bean's attribute injection

1. Construction Method Injection

Provides construction methods

Public Userserviceimp (String name) {super (); this.name = name;}

Modify the Applicationcontext.xml file

<bean id= "UserService" class= "com.baidu.test.UserServiceImp" >    <constructor-arg index= "0" value= "Zhang San" Type= "Java.lang.String" ></constructor-arg>
</bean>    

2.Setter Injection

Modify Applicationcontext.xml

<bean id= "user" class= "com.baidu.test.User" >        <property name= "name" value= "UUU" ></property>        <property name= "age" value= "></property></bean>        <bean id=" UserService "class=" Com.baidu.test.UserServiceImp ">        <property name=" name "value=" UU "></property>        <property Name= "U" ref= "user" ></property>// introduce another bean        </bean>

3.map Injection

 <bean id= "user" class= "com.baidu.test.User" > <property name= "NA          Me "value=" UUU "></property> <property name=" age "value=" ></property></bean> "        <bean id= "UserService" class= "com.baidu.test.UserServiceImp" > <property name= "name" value= "UU" > </property> <property name= "list" > <list> <value>10</value> < Value> Zhang San </value> <ref bean= "user"/> </list> </property> <propert Y name= "set" > <set> <value> Zhang San </value> <ref bean= "user"/> </SET&G        T </property> <property name= "map" > <map> <entry key= "1" value-ref= "user" ></ Entry> <entry key= "2" value= "></entry>" </map> </property> </b Ean> 

　Space names P and C

Introduction of Schma

　　　　  Xmlns:c= "http://www.springframework.org/schema/c" xmlns:p= "http://www.springframework.org/schema/p"

First they are not real namespaces, they are virtual. It is embedded in the spring kernel. Using the P-namespace can solve our setter injection <property> simplify     using C namespace can solve our constructor injection when <constructor-arg> simplify

Applicationcontext.xml

P namespace---------Setter injection

<bean id= "user" class= "com.baidu.test.User" >        <property name= "name" value= "UUU" ></property>        p:u-ref= "user" >        </bean>

　　

C namespace-------Constructor injection

<bean id= "UserService" class= "com.baidu.test.UserServiceImp" c:name= "UU" c:u-ref= "user" > </bean>

Spel (Spring expression Language) Spring 3.0 version

It is similar to the OGNL or El expression, which provides the ability to construct complex expressions to complete object property storage and method invocation when the program is run. Spel expression format #{expression}

Applicationcontext.xml

1. Complete the injection between the beans

<bean id= "user" class= "com.baidu.test.User" >        <property name= "name" value= "UUU" ></property>        <property name= "age" value= "></property></bean> <bean id=" UserService "class=" Com.baidu.test.UserServiceImp ">         <property name=" name "value=" UU "></property>
<!--<property name= "u" ref= "user" ></property>->        <property name= "u" value= "#{user}" > </property> overrides the above ref value (completes the injection between beans)        </bean>

2. Support for property invocation and called method invocation

<bean id= "user" class= "com.baidu.test.User" >        <property name= "name" value= "UUU" ></property>        <property name= "age" value= "></property></bean><bean id=" user1 "class=" Com.baidu.test.User ">        <property name=" name "value=" UUU "></property>        <property name=" age "Value=" #{user.getage () +5} "></property></bean> <bean id=" UserService "class=" Com.baidu.test.UserServiceImp ">         <property name=" name "value=" UU "></property>        <property Name= "U" value= "#{user1}" ></property>        </bean>

　　

　　

Spring Config Bean