本篇文章主要介绍了Spring依赖注入的三种方式小结，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧
目录
具体步骤：
样例1：
样例2：
Spring单例模式和原型模式
一、单例模式
二、原型模式
思考 为什么需要依赖注入
总结
具体步骤：
1.创建一个maven项目 spring-day1-constructor
2.导入依赖
UTF-811115.3.11.18.204.12org.springframeworkspring-beans${spring.version}org.springframeworkspring-context${spring.version}org.projectlomboklombok${lombok.version}junitjunit${junit.version}
3.工程项目结构
样例1：
1.创建一个Student类
public class Student { private Long number; private String name; private String school; public void setNumber(Long number) { this.number = number; } public void setName(String name) { this.name = name; } public void setSchool(String school) { this.school = school; } public Student() { } public Student(Long number, String name, String school) { this.number = number; this.name = name; this.school = school; } @Override public String toString() { return "Student{" + "number=" + number + ", name='" + name + ''' + ", school='" + school + ''' + '}'; } }
3.测试
@org.junit.Test public void testStudent(){ ApplicationContext applicationContext = new ClasspathXmlApplicationContext("beans.xml"); Student student = applicationContext.getBean("s2", Student.class); System.out.println(student); }
样例2：
1.创建Teacher类
public class Teacher { private String name; private String school; private List studentList; private Map map; private Set set; public Teacher(String name, String school, List studentList, Map map, Set set) { this.name = name; this.school = school; this.studentList = studentList; this.map = map; this.set = set; } @Override public String toString() { return "Teacher{" + "name='" + name + ''' + ", school='" + school + ''' + ", studentList=" + studentList + ", map=" + map + ", set=" + set + '}'; } }public class Teacher { private String name; private String school; private List studentList; private Map map; private Set set; public Teacher(String name, String school, List studentList, Map map, Set set) { this.name = name; this.school = school; this.studentList = studentList; this.map = map; this.set = set; } @Override public String toString() { return "Teacher{" + "name='" + name + ''' + ", school='" + school + ''' + ", studentList=" + studentList + ", map=" + map + ", set=" + set + '}'; } }
2.beans.xml
12
3.测试
@org.junit.Test public void testTeacher(){ ApplicationContext applicationContext = new ClasspathXmlApplicationContext("beans.xml"); Teacher teacher = applicationContext.getBean("teacher", Teacher.class); System.out.println(teacher); }
Spring单例模式和原型模式
一、单例模式
Spring默认是单例模式的。
以Student的那个样例1 为例。 scope=“singleton” 加上这么一个设置 当然默认也是它。
bean id="s1" class="com.crush.pojo.Student" scope="singleton">
这个时候我们来进行测试
@org.junit.Test public void testStudent(){ ApplicationContext applicationContext = new ClasspathXmlApplicationContext("beans.xml"); Student student1 = applicationContext.getBean("s1", Student.class); Student student2 = applicationContext.getBean("s1", Student.class); // 并且如果我们对其中一个做了修改 ，其余也会跟着一起被修改 // 可以看到我们只修改了一个 student1.setSchool("梦中的学校"); System.out.println(student1); System.out.println(student2); System.out.println(student1==student2); }
二、原型模式
我们还是以**Student来做例子讲解 ** 注意：我们把原来设置改成了 scope=“prototype” 也就是原型模式
接着测试
@org.junit.Test public void testStudent(){ ApplicationContext applicationContext = new ClasspathXmlApplicationContext("beans.xml"); Student student1 = applicationContext.getBean("s2", Student.class); Student student2 = applicationContext.getBean("s2", Student.class); // 并且如果我们对其中一个做了修改 ，其余也会跟着一起被修改 // 可以看到我们只修改了一个 student1.setSchool("梦中的学校"); System.out.println(student1); System.out.println(student2); System.out.println(student1==student2); }
思考 为什么需要依赖注入
为什么我们以前用一个对象 new一下就好了，但用了Spring 之后，反而还需要写
这样一段代码再去获取勒？明明感觉更麻烦啦丫？用这个又有什么样的好处呢？
ApplicationContext applicationContext = new ClasspathXmlApplicationContext("beans.xml"); Student student1 = applicationContext.getBean("s2", Student.class);
