Spring学习（二）

为什么要是用Spring依赖注入：
平常的java开发中，程序员在某个类中需要依赖其它类的方法，则通常是new一个依赖类再调用类实例的方法，这种开发存在的问题是new的类实例不好统一管理，spring提出了依赖注入的思想，即依赖类不由程序员实例化，而是通过spring容器帮我们new指定实例并且将实例注入到需要该对象的类中。依赖注入的另一种说法是“控制反转”，通俗的理解是：平常我们new一个实例，这个实例的控制权是我们程序员，而控制反转是指new实例工作不由我们程序员来做而是交给spring容器来做

关于Spring的属性注入一共有两种方式，分别为XML方式与注解方式，其中XML方式又分为Set注入与构造方法注入，注解方式分为java注解与Spring注解

一、使用属性注入

package com.shuxing.bean;

public interface StudentDao {

    public boolean saveStudent(Student student);
}

package com.shuxing.bean;

public class StudentDaoImpl implements StudentDao{

    @Override
    public boolean saveStudent(Student student) {

        if(student!=null)
        {
            System.out.println("学号："+student.getPersonid());
            System.out.println("名字: "+student.getName());
            System.out.println("年龄："+student.getAge());
            return true;
        }
        else
            return false;
    }

}

package com.shuxing.bean;

public interface StudentService {

    public boolean saveStudent();
}

package com.shuxing.bean;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao;
    private Student student;
    public StudentServiceImpl() {   
    }
    public StudentServiceImpl(StudentDao studentDao) {
        this.studentDao = studentDao;
    }
    @Override
    public boolean saveStudent() {
        if(studentDao.saveStudent(student)) {
            return true;
        }
        else
            return false;   
    }
    public StudentDao getStudentDao() {
        return studentDao;
    }
    public void setStudentDao(StudentDao studentDao) {
        this.studentDao = studentDao;
    }
    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
}

测试类

package com.shuxing.bean;

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

public class TestSaveStudent {

    public static void main(String[] args) {
        //读取配置文件
        ApplicationContext ctx=new 
                ClassPathXmlApplicationContext("springXML/beans.xml");
        Student student=(Student)ctx.getBean("student");
        student.setPersonid("1001");
        student.setName("zhangsan");
        student.setAge(20);
        //获取对象
        StudentServiceImpl service=(StudentServiceImpl)ctx.getBean("studentService");
        if(service.saveStudent()) {
            System.out.println("操作成功");
        }
        else {
            System.out.println("操作失败");
        }
    }

}

二、构造方法注入

package com.shuxing.bean;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao;
    private Student student;
    public StudentServiceImpl() {   
    }

    public StudentServiceImpl(StudentDao studentDao, Student student) {

        this.studentDao = studentDao;
        this.student = student;
    }


    @Override
    public boolean saveStudent() {
        if(studentDao.saveStudent(student)) {
            return true;
        }
        else
            return false;   
    }
    /*
    public StudentDao getStudentDao() {
        return studentDao;
    }
    public void setStudentDao(StudentDao studentDao) {
        this.studentDao = studentDao;
    }
    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
    */
}

bean.xml文件

<?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-3.0.xsd">

    <bean id="helloWorld" class="com.firstSpring.HelloWorldImpl"></bean>

    <bean name="student" class="com.shuxing.bean.Student"></bean>
    <bean name="studentDao" class="com.shuxing.bean.StudentDaoImpl"></bean>
    <bean name="studentService" class="com.shuxing.bean.StudentServiceImpl">
        <!-- 1、Setter属性注入 -->  
        <!-- <property name="属性名称" ref="bean引用名称"></property> --> 
        <!--  
        <property name="studentDao" ref="studentDao"></property>
        <property name="student" ref="student"></property>
        -->


        <!-- 2、构造方法注入 -->  
        <!-- <constructor-arg ref="bean引用名称" index="属性索引"></constructor-arg> -->  
        <constructor-arg ref="studentDao" index="0"></constructor-arg>  
        <constructor-arg ref="student" index="1"></constructor-arg>
    </bean> 
</beans>