Spring之Bean的装配[通俗易懂]

大家好，又见面了，我是你们的朋友全栈君。

Spring装配工厂是为了兼容以前没有Spring的时候，已经写好的工厂代码。
装配
set装配：property
构造装配：constructor-arg
集合装配：Aray List Set 但实际上是通用的

Bean的装配可以理解为依赖关系注入Bean的装配方式即Bean依赖注入的方式.Spring容器支持多种形式的Bean的装配方式，如基于XML的装配、基于注解（Annotation）的装配和自动装配（其中最常用的是基于注解的装配）
需要引入的jar包：

  <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

多例和单例

public static void main(String[] args){ 
   
       ApplicationContext context= new ClassPathXmlApplicationContext("spring/applicationContext.xml");
       UserService userService=context.getBean("userService",UserService.class);
       UserService userService2=context.getBean("userService",UserService.class);
       System.out.println(userService.hashCode());
       System.out.println(userService2.hashCode());
   }

spring 容器获得的对象 默认是单例的，如有必要可以在配置文件中修改为多例

<bean class="com.xbj.service.UserServiceImpl" id="userService" scope="prototype">
        <!--如果设置了setter 方法 就会提示  ref 引用得是被管理的对象 value 是设置普通值-->
        <property name="userDAO" ref="userDAO"/>
</bean>

Bean 的初始化时机
默认情况下，Spring bean的初始化时机，是容器启动的时候，而不是 对象被调用的时候
但是如果一个Bean被设置为多例的，Bean使用的时候才会被创造

装配工厂

非静态方法：必须实例化工厂类（factory-bean）后才能调用工厂方法
实例工厂

public class DAOFactory { 
   
   public TopicDAO getTopicDAO(){ 
   
       return new TopicDAOImpl();
   }
   public UserDAO getUserDAO(){ 
   
       return new UserDAOImpl();
   }
}

<! --装配实例工厂-->
<bean class="com.xbj.factory.DAOFactory" id="daoFactory"/>
<!--装配Bean -->
<bean id="userDAO" factory-bean="daoFactory" factory-method="getUserDAO"/>
<bean id="topicDAO" factory-bean="daoFactory" factory-method="getTopicDAO"/>

静态方法：无须创建工厂类实例的情况下就可以调用工厂类方法

//静态工厂
public class DAOFactory { 
   
    public static TopicDAO getTopicDAO(){ 
   
        return new TopicDAOImpl();
    }
    public static UserDAO getUserDAO(){ 
   
        return new UserDAOImpl();
    }
}
public class UserServiceImpl implements UserService{ 
   
    private UserDAO userDAO=DAOFactory.getUserDAO();
    private TopicDAO topicDAO=DAOFactory.getTopicDAO();
    public void addUser() { 
   
        userDAO.addUser();
    }
    public void delUser() { 
   
        userDAO.delUser();
    }
    //setter 初始化 UserDAO
    public void setUserDAO(UserDAO userDAO) { 
   
        System.out.println("通过setter");
        this.userDAO = userDAO;
    }

<!--装配Bean -->
<bean id="userDAO" class="com.xbj.factory.DAOFactory" factory-method="getUserDAO"/>
<bean id="topicDAO" class="com.xbj.factory.DAOFactory" factory-method="getTopicDAO"/>

factory-bean：用于实例化工厂类；
factory-method：用于调用工厂类方法。

Set方法装配

    package com.xbj.po;
    public class Address {
        private String city;
        private String area;
        private Integer code;
       //getter setter
    }

package com.xbj.po;
   public class User {
       private String name;
       private Integer age;
       private Address address;
       //getter setter 
   }

    <?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="
            http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd">
        <bean class="com.xbj.po.Address" id="address">
            <property name="city" value="HF"/>
            <property name="area" value="SS" />
            <property name="code" value="100100" />
        </bean>
        <bean class="com.xbj.po.User" id="user">
            <property name="name" value="tom"/>
            <property name="address" ref="address"/>
            <property name="age" value="22" />
        </bean>
    </beans>

public class Test01 {
   @Test
   public void t1(){
       ApplicationContext context=new ClassPathXmlApplicationContext("spring/applicationContext.xml");
       User user=context.getBean("user", User.class);
       System.out.println(user.getName());
   }
   @Test
   public void t2(){
       ApplicationContext context=new ClassPathXmlApplicationContext("spring/applicationContext.xml");
       User user=context.getBean("user", User.class);
       System.out.println(user.getAddress().getCity());
   }
   @Test
   public void t3(){
   }
}

构造装配

默认情况下（没有指定特定的构造装配Bean） Spring容器 通过 空构造 创造对象，如果没有空构造，会报错：找不到默认的构造

public class Address {
    private String city;
    private String area;
    private Integer code;
    public Address() {
    }
    public Address(String area, Integer code) {
        this.area = area;
        this.code = code;
    }
    public Address(String city, String area) {
        this.city = city;
        this.area = area;
    }
 //getter  setter

//applicationContext.xml
   <bean class="com.xbj.po.Address" id="address">
           <constructor-arg value="HF" name="area" />
           <constructor-arg value="22" name="code" />
   </bean>

//Junit 注解  的方法必须是public的   
 private  ApplicationContext context;
   @Before
   public void init(){
       context=new ClassPathXmlApplicationContext("spring/applicationContext-2.xml");
   }
   @Test
   public void t1(){
       Address address=context.getBean("address", Address.class);
       System.out.println(address);
   }

P命名空间

简化setter方法的装配

public class Address {
   private String city;
   private String area;
   private Integer code; 
  //getter  setter

    <bean class="com.xbj.po.Address" id="address">
        <property name="city" value="HF"/>
        <property name="area" value="SS" />
        <property name="code" value="100100" />
    </bean>
    <bean class="com.mchange.v2.c3p0.ComboPooledDataSource" id="comboPooledDataSource">
        <property name="jdbcUrl" value=""  />
        <property name="password" value=" " />
        <property name="user" value="" />
        <property name="driverClass" value=""/>
    </bean>
 

约束文件添加         xmlns:p="http://www.springframework.org/schema/p"
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:p="http://www.springframework.org/schema/p"
      xsi:schemaLocation="
       http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd">
   <bean class="com.xbj.po.Address" id="address" p:area="SS" p:city="HF" p:code="100100" />
     <bean class="com.mchange.v2.c3p0.ComboPooledDataSource" id="comboPooledDataSource" p:jdbcUrl=""
         p:driverClass="" p:user="" p:password=""  />

3.6 集合的装配

装配 List Set Array

public class User
{
    private  List<String> hobbies;
    private String[] books;
    private Set<Integer> nums;
 //getter  setter

<bean class="com.xbj.po.User" id="user">
        <!--集合装配  List  Set Array （list-set-array 是通用的）-->
        <property name="books" >
            <array>
                <value>sanguo</value>
                <value>shuihu</value>
            </array>
        </property>
        <property name="hobbies">
            <list>
                <value>11</value>
                <value>22</value>
            </list>
        </property>
        <property name="nums">
            <list>
                <value>11</value>
                <value>22</value>
            </list>
        </property>
    </bean>

装配

public class User{
    private  List<String> hobbies;
    private String[] books;
    private Set<Integer> nums;
    private HashMap<String,String> likes;
  //getter setter

<property name="likes">
          <map>
              <entry key="lucy" value="ddd"/>
              <entry key="lucy2" value="3333"/>
          </map>
</property>

private Properties props;
的本质也是MAP 可以按照MAP去装配