初学Spring

Spring是当今最流行的框架，今天开始，dayday同学要正式开始学习Spring了，加油

以下是一个简单的应用Spring框架的java程序

src\dayday\HelloSpring.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class HelloSpring {
    private String name;
    public void setName(String name){
        this.name=name;
    }
    public void println(){
        System.out.println("hello "+name+" ,study Spring hard!!!");
    }
}

src\dayday\Main.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class Main {
    public static void main(String[] args){
        //获得Spring容器
        ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
       // 获得一个bean,spring中所有的java类都为bean
        HelloSpring hellospring=ctx.getBean("hellospring",HelloSpring.class);
        //调用类中的方法
        hellospring.println();
       // 原来不用spring框架的时候,将得到同样的运行结果
        HelloSpring hellospring=new HelloSpring();
        helloSpring.setName("dayday");
        hellospring.println();
    }

}

src\beans.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    //调用反射调用该类的无参构造函数创建一个bean(对象)，必须要有包，id为创建bean(类)的名字
    //name中的值（String）会相应的调用类中setString()的方法，value表示对应属性的值，也可以是ref,ref中是另外一个bean
    <bean id="hellospring" class="dayday.HelloSpring">  
        <property name="name" value="dayday"/>
    </bean>
   //另外一种方式，通过p标签进行配置，如果要通过p标签配置的话，bean中不能含有有参构造函数

    <!--通过p标签进行配置-->
    <bean name="hellospring" class="dayday.HelloSpring" p:name="dayday" p:book-ref="book"/>
    <bean name="book" class="dayday.Book" p:bookname="《Spring MVC》"/>

</beans>

运行结果
hello dayday ,study Spring hard!!!

<property>中使用ref
src\dayday\HelloSpring.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class HelloSpring {
    private Book book;
    private String name;
    public void setName(String name){
        this.name=name;
    }
    public void setBook(Book book){
        this.book=book;
    }
    public void println(){
        System.out.println("hello "+name+" ,study Spring hard!!!"+book.print());
    }

    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
        HelloSpring hellospring=ctx.getBean("hellospring",HelloSpring.class);
        hellospring.println();
    }

}

src\dayday\Book.java

package dayday;

/**
 * Created by I am master on 2016/11/28.
 */
public class Book {
    private String bookname;
    public void setBookname(String bookname){
        this.bookname=bookname;
    }
    public String print(){
       return "read "+bookname;
    }
}

src\dayday\Main.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class Main {
    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
        HelloSpring hellospring=ctx.getBean("hellospring",HelloSpring.class);
        hellospring.println();
    }

}

src\dayday\beans.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="hellospring" class="dayday.HelloSpring">
        <property name="name" value="dayday"/>
        <property name="book" ref="book"></property>
    </bean>
    <bean id="book" class="dayday.Book">
        <property name="bookname" value="《Spring mvc》"></property>
    </bean>
</beans>

通过构造注入，之前的都为设值注入
//若通过构造注入，bean(java类)中必须要有构造函数
通过<constructor-arg.../>注入，value="String等基本类型" ref=“bean”
可以通过index属性指定构造参数值将作为第几个构造参数值，index="0"表明作为第一个构造函数参数值，错位开了
一般采用设值注入为主，构造注入为辅
src\dayday\HelloSpring.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class HelloSpring {
    private Book book;
    private String name;

    public  HelloSpring(String name,Book book){
        this.name=name;
        this.book=book;
    }
    public void println(){
        System.out.println("hello "+name+" ,study Spring hard!!!"+book.print());
    }

    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
        HelloSpring hellospring=ctx.getBean("hellospring",HelloSpring.class);
        hellospring.println();
    }

}

src\dayday\Book.java

package dayday;

/**
 * Created by I am master on 2016/11/28.
 */
public class Book {
    private String bookname;
    public Book(String bookname){
           this.bookname=bookname;
    }
    public String print(){
       return "read "+bookname;
    }
}

src\dayday\Main.java

package dayday;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by I am master on 2016/11/28.
 */
public class Main {
    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
        HelloSpring hellospring=ctx.getBean("hellospring",HelloSpring.class);
        hellospring.println();
    }

}

src\dayday\beans.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="hellospring" class="dayday.HelloSpring">
        <constructor-arg value="dayday"></constructor-arg>
        <constructor-arg ref="book"></constructor-arg>
    </bean>
    <bean id="book" class="dayday.Book">
        <constructor-arg value="《Spring MVC》"></constructor-arg>
    </bean>
</beans>

bean作用域的配置 
用scope属性来配置bean的作用域
Singleton:默认值，容器初始时创建bean实例
（在执行 <bean id="hellospring" class="dayday.HelloSpring">这句是调用无参构造函数创建）
在整个容器的生命周期内只创建这一个bean，单例的
常用的还有prototype,每次调用getbean()方法就调用构造函数创建一个bean