1,Set注入 2,构造注入
Set方法注入:
原理:通过类的setter方法完成依赖关系的设置
name属性的取值依setter方法名而定,要求这个类里面这个对应的属性必须有setter方法。
Set方法注入时spring中配置文件:
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<? 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 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> < bean id = "car" class = "org.spring01.Car" > < constructor-arg value = "奔驰" ></ constructor-arg > < constructor-arg type = "java.lang.String" > < value >土豪金</ value > </ constructor-arg > < constructor-arg value = "高级轿车" ></ constructor-arg > </ bean > < bean id = "person" class = "org.spring01.Person" > < property name = "name" value = "张三" ></ property > < property name = "age" value = "11" ></ property > < property name = "car" ref = "car" ></ property > </ bean > </ beans > |
定义Car类:
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package org.spring01; public class Car { private String name; //车名 private String color; //颜色 private String clas; //等级 public String getName() { return name; } public void setName(String name) { this .name = name; } public String getColor() { return color; } public void setColor(String color) { this .color = color; } public String getClas() { return clas; } public void setClas(String clas) { this .clas = clas; } public Car(String name, String color, String clas) { super (); this .name = name; this .color = color; this .clas = clas; } public Car() { super (); // TODO Auto-generated constructor stub } @Override public String toString() { return "Car [name=" + name + ", color=" + color + ", clas=" + clas + "]" ; } } |
定义Person类:
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package org.spring01; public class Person { private String name; //名字 private int age; //年龄 private Car car; //他的车 public String getName() { return name; } public void setName(String name) { this .name = name; } public int getAge() { return age; } public void setAge( int age) { this .age = age; } public Car getCar() { return car; } public void setCar(Car car) { this .car = car; } public Person(String name, int age, Car car) { super (); this .name = name; this .age = age; this .car = car; } public Person() { super (); // TODO Auto-generated constructor stub } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", car=" + car + "]" ; } } |
测试类:
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package org.spring01; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class SpringTest{ @Test public void toGetPerson(){ ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext.xml" ); Person person = (Person) context.getBean( "person" ); System.out.println(person); } @Test public void toGetCar(){ ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext.xml" ); Car car = (Car) context.getBean( "car" ); System.out.println(car); } } |
使用单元测试(JUnit)测试toGetPerson()方法,结果为:
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Person [name=张三, age=11, car=Car [name=奔驰, color=土豪金, clas=高级轿车]] |
构造方法注入:
原理:通过构造函数完成依赖关系的设定
构造注入指的是在接受注入的类中,定义一个构造方法,并在构造方法的参数中定义需要注入的元素,其中,index表示构造方法中的参数索引(第一个参数索引为0)。
构造方法注入时spring中配置文件:
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<? 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 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> < bean id = "car" class = "org.spring02.Car" > < constructor-arg value = "大众" ></ constructor-arg > < constructor-arg type = "java.lang.String" > < value >白色</ value > </ constructor-arg > < constructor-arg value = "中级轿车" ></ constructor-arg > </ bean > < bean id = "person" class = "org.spring02.Person" > < constructor-arg index = "0" value = "李四" ></ constructor-arg > < constructor-arg index = "1" value = "23" ></ constructor-arg > < constructor-arg index = "2" ref = "car" ></ constructor-arg > </ bean > </ beans > |
定义Car类:
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package org.spring02; public class Car { private String name; //车名 private String color; //颜色 private String clas; //等级 public Car(String name, String color, String clas) { super (); this .name = name; this .color = color; this .clas = clas; } public Car() { super (); // TODO Auto-generated constructor stub } @Override public String toString() { return "Car [name=" + name + ", color=" + color + ", clas=" + clas + "]" ; } } |
定义Person类:
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package org.spring02; public class Person { private String name; //名字 private int age; //年龄 private Car car; //他的车 public Person(String name, int age, Car car) { super (); this .name = name; this .age = age; this .car = car; } public Person() { super (); // TODO Auto-generated constructor stub } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", car=" + car + "]" ; } } |
测试类:
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package org.spring02; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class SpringTest{ @Test public void toGetPerson(){ ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext01.xml" ); Person person = (Person) context.getBean( "person" ); System.out.println(person); } @Test public void toGetCar(){ ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext01.xml" ); Car car = (Car) context.getBean( "car" ); System.out.println(car); } } |
使用单元测试(JUnit)测试toGetPerson()方法,结果为:
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Person [name=李四, age=23, car=Car [name=大众, color=白色, clas=中级轿车]] |
上面的例子都采用了单元测试的方法检测运行结果,需要导库: JUnit
Demo的大体结构:
我们可以看到,set方法和构造方法都可以设值成功, 实际开发中最常用到的是set方法设值。但这两种依赖注入的方式并没有绝对的好坏,只是使用的场合不同。
使用构造注入可以在构建对象的同时完成依赖关系到的建立,所以如果要建立的对象的关系很多,使用构造注入会在构造方法上留下很多参数,可读性极差,所以当对象的关系比较多的时候采用set方法注入。
使用set方法注入是通过类的setter方法完成依赖关系的设置的,所以不能保证相关的数据在执行时不被更改设定。所以如果想使一些数据变为只读或者私有,就要采用构造注入了。
建议采用以set注入为主,构造注入为辅的注入策略。对于依赖关系无须变化的注入,尽量采用构造注入;而其他的依赖关系的注入,则考虑采用set注入。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。
原文链接:http://blog.csdn.net/weixin_36380516/article/details/72301260?utm_source=tuicool&utm_medium=referral