Spring框架总结(三)

SpringIOC容器

一、创建对象

SpringIOC容器，是spring核心内容。

作用： 创建对象 & 处理对象的依赖关系

IOC容器创建对象：

创建对象, 有几种方式：

1） 调用无参数构造器

2） 带参数构造器

3） 工厂创建对象

工厂类，静态方法创建对象

工厂类，非静态方法创建对象

事例一：构造函数是无参

创建一个无参构造函数

需要三个部分

User

 public class User {

     public User() {
         System.out.println("======不带参构造器=========");
     }

     public User(String userId, String username) {
         System.out.println("======带参构造器=========");
         this.userId = userId;
         this.username = username;
     }

     public User(String userId, String username, String string) {
         System.out.println("======带参构造器2=========");
         this.userId = userId;
         this.username = username;
     }

     private String userId;
     private String username;

     public String getUserId() {
         return userId;
     }

     public void setUserId(String userId) {
         this.userId = userId;
     }

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     @Override
     public String toString() {
         return "User [userId=" + userId + ", username=" + username + "]";
     }

 }

bean.xml

 <?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"
     xmlns:context="http://www.springframework.org/schema/context"
     xsi:schemaLocation="
         http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context.xsd">

     <!-- 无参构造函数的 -->
     <bean id="user1" class="com.liuyang.constructor.User">
     </bean>
 </beans>

测试类

 public class App {

     ApplicationContext aContext = new ClassPathXmlApplicationContext(
             "com/liuyang/constructor/beans.xml");

     @Test
     public void test() {
         User user = (User) aContext.getBean("user");

         System.out.println(user);
     }
 }

事例二：构造函数是带参

更改bean.xml为如下,其他不变

<?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"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 带构造函数的 -->
    <bean id="user1" class="com.liuyang.constructor.User">
        <constructor-arg value="100" index="0" type="java.lang.String"></constructor-arg>
        <constructor-arg value="Jack" index="1" type="java.lang.String"></constructor-arg>
</bean>
</beans>

事例三:外部引用,定义一个字符串外部引入类中(xml实现)

<?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"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
<!--定义一个字符串类型 相当于new String("whiteRabbit")-->
<bean id="str" class="java.lang.String">
        <constructor-arg value="whiteRabbit"></constructor-arg>
    </bean>
<bean id="user1" class="com.liuyang.constructor.User">
        <constructor-arg value="100" index="0" type="java.lang.String"></constructor-arg>
        <constructor-arg value="Jack" index="1" type="java.lang.String"></constructor-arg>
        <constructor-arg index="2" type="java.lang.String"
            ref="str"></constructor-arg>

    </bean>
</beans>

事例四:向类中插入值

更改bean.xml为如下

<?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"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 向对象中传值 -->
    <bean id="str" class="java.lang.String">
        <constructor-arg value="whiteRabbit"></constructor-arg>
    </bean>
    <bean id="user" class="com.liuyang.constructor.User">
        <constructor-arg index="0" type="java.lang.String"
            value="100"></constructor-arg>
        <constructor-arg index="1" type="java.lang.String"
            ref="str"></constructor-arg>
    </bean>
</beans>

事例五:工厂创建对象和静态调用

1、user不变

2、创建类ObjectFactory

 public class ObjectFactory {

     public User getInstance() {

         return new User("100", "=====实例化一个对象=========");

     }

     public static User getStaticInstance() {
         return new User("101", "=====静态方法调用=========");

     }

 }

3、更改bean.xml为如下

 <?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"
     xmlns:context="http://www.springframework.org/schema/context"
     xsi:schemaLocation="
         http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context.xsd">

     <!-- 实例化一个对象 -->
     <bean id="oFactory" class="com.liuyang.static1.constructor.ObjectFactory">
     </bean>
     <bean id="user" factory-bean="oFactory" factory-method="getInstance"></bean>

     <!-- 静态方法调用 -->
     <bean id="user2" class="com.liuyang.static1.constructor.ObjectFactory"
         factory-method="getStaticInstance"></bean>
 </beans>

4、测试

 public class App {

     ApplicationContext aContext = new ClassPathXmlApplicationContext(
             "com/liuyang/static1/constructor/beans2.xml");

     @Test
     public void test() {
         User user = (User) aContext.getBean("user");

         System.out.println(user);
     }

     @Test
     public void test2() {
         User user2 = (User) aContext.getBean("user2");

         System.out.println(user2);
     }
 }