Spring框架入门之基于xml文件配置bean详解

关于Spring中基于xml文件配置bean的详细总结（spring 4.1.0）

一、Spring中的依赖注入方式介绍

　　依赖注入有三种方式

• 属性注入
• 构造方法注入
• 工厂方法注入（很少使用，不推荐，本文不再介绍）

　　属性注入

  通过 setter 方法注入Bean 的属性值或依赖的对象。属性注入使用 <property>元素, 使用 name 属性指定 Bean 的属性名称，value 属性或 <value> 子节点指定属性值 。属性注入是实际应用中最常用的注入方式。HelloWorld类中的setName()方法，对应上边代码中的name属性，例如：把setName()方法名改为setName2()，property中的name属性值为name时则会报错，需要将name属性改为name2。

---

　　构造方法

  构造方法注入Bean 的属性值或依赖的对象，它保证了 Bean 实例在实例化后就可以使用。
  构造器注入在 <constructor-arg> 元素里声明属性, <constructor-arg> 中没有 name 属性。使用value属性值或value子节点为属性赋值。可以同时使用索引 index 和type属性对应为哪个属性赋值。index的值表示构造函数中参数的位置。type表示成员属性的类型，例如type=“double”

二、属性注入和构造方法注入详解：

1.applicationContext.xml文件配置如下

 <?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:util="http://www.springframework.org/schema/util"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
         http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.1.xsd">

     <!--
         配置bean
         class:bean的全类名，通过反射的方式在IOC容器中创建bean
         id：表示容器中的bean，id唯一
     -->
     <!-- 通过setter注入配置bean的属性 -->
     <bean id="helloWorld" class="me.spring.beans.HelloWorld">
         <property name="name" value="Spring"></property>
     </bean>
     <!-- 通过构造方法配置bean的属性 -->
     <bean id="car" class="me.spring.beans.Car">
         <constructor-arg value="Audi"></constructor-arg>
         <constructor-arg value="ShangHai"></constructor-arg>
         <constructor-arg value="300000"></constructor-arg>
     </bean>

     <!--
         使用构造器注入的属性值可以指定参数的类型和参数的位置，以区分重载的构造器
         如果字面值包含特殊字符，可以使用<![CDATA[]]>包裹起来
         属性值也可以使用value子节点进行配置
      -->
     <bean id="car2" class="me.spring.beans.Car">
         <constructor-arg value="Baoma"></constructor-arg>
         <constructor-arg type="java.lang.String">
             <value><![CDATA[<Beijing>]]></value>
         </constructor-arg>
         <constructor-arg value="240" type="int"></constructor-arg>
     </bean>

     <!-- 可以使用property的ref属性建立bean之间的引用关系 -->
     <bean id="person" class="me.spring.beans.Person">
         <property name="name" value="Tom"></property>
         <property name="age" value="24"></property>
         <!--
         <property name="car" ref="car2"></property>
          -->

         <!--
         <property name="car">
             <ref bean="car2"/>
         </property>
         -->

         <!-- 内部bean，不能被外部引用 -->
         <property name="car">
             <bean class="me.spring.beans.Car">
                 <constructor-arg value="Ford"></constructor-arg>
                 <constructor-arg value="ChangAn"></constructor-arg>
                 <constructor-arg value="2354395" type="double"></constructor-arg>
             </bean>
         </property>
     </bean>

     <bean id="person2" class="me.spring.beans.Person">
         <constructor-arg value="Jerry"></constructor-arg>
         <constructor-arg value="25"></constructor-arg>
         <constructor-arg ref="car2"></constructor-arg>

         <!-- 测试赋值null -->
         <!--
         <constructor-arg><null/></constructor-arg>
         -->
         <!--
             为级联属性赋值
             注意:属性需要初始化后才可以为级联属性赋值，和Struts2不同
             这里必须依据person的setter和getter方法，不能为car2
         -->
         <property name="car.price" value="4546"></property>
     </bean>

     <!-- 测试如何配置集合属性 -->
     <bean id="person3" class="me.spring.beans.collections.Person">
         <property name="name" value="Mike"></property>
         <property name="age" value="34"></property>
         <property name="cars">
         <!-- 使用list结点为属性为list的属性赋值 -->
             <list>
                 <ref bean="car"/>
                 <ref bean="car2"/>
                 <bean class="me.spring.beans.Car">
                     <constructor-arg value="Ford"></constructor-arg>
                     <constructor-arg value="ChangAn"></constructor-arg>
                     <constructor-arg value="2354395" type="double"></constructor-arg>
                 </bean>
             </list>
         </property>
     </bean>
     <bean id="newPerson" class="me.spring.beans.collections.NewPerson">
         <property name="name" value="Rose"></property>
         <property name="age" value="23"></property>
         <property name="cars">
         <!-- 使用map结点及map的entry子节点配置Map类型的成员变量 -->
             <map>
                 <entry key="AA" value-ref="car"></entry>
                 <entry key="BB" value-ref="car2"></entry>
             </map>
         </property>
     </bean>

     <!-- 配置properties属性值 -->
     <bean id="dataSource" class="me.spring.beans.collections.DataSource">
         <property name="properties">
         <!-- 使用props和prop子节点来为properties属性值赋值 -->
             <props>
                 <prop key="user">root</prop>
                 <prop key="password">123456</prop>
                 <prop key="jdbcURL">jdbc:mysql://localhost:3306/test</prop>
                 <prop key="driverClass">com.mysql.jdbc.Driver</prop>
             </props>
         </property>
     </bean>

     <!-- 配置单例的集合bean，以供多个bean进行引用，需要导入util命名空间 -->
     <util:list id="cars">
         <ref bean="car"/>
         <ref bean="car2"/>
     </util:list>

     <bean id="person4" class="me.spring.beans.collections.Person">
         <property name="name" value="Jack"></property>
         <property name="age" value="34"></property>
         <property name="cars" ref="cars"></property>
     </bean>

     <!-- 通过p命名空间为bean的属性赋值，需要导入p命名空间,相对于传统的配置较为简洁 -->
     <bean id="person5" class="me.spring.beans.collections.Person" p:name="Queen" p:age="45" p:cars-ref="cars"></bean>
 </beans>

2.相关的实体类：

(1)me.spring.beans 包下：

 package me.spring.beans;

 public class Car {

     private String brand;
     private String corp;
     private double price;
     private int maxSpeed;
     public Car(String brand, String corp, double price) {
         super();
         this.brand = brand;
         this.corp = corp;
         this.price = price;
     }

     public Car(String brand, String corp, int maxSpeed) {
         super();
         this.brand = brand;
         this.corp = corp;
         this.maxSpeed = maxSpeed;
     }

     public void setPrice(double price) {
         this.price = price;
     }

     public double getPrice() {
         return price;
     }
     @Override
     public String toString() {
         return "Car [brand=" + brand + ", corp=" + corp + ", price=" + price + ", maxSpeed=" + maxSpeed + "]";
     }

 }

 package me.spring.beans;

 public class Person {

     private String name;
     private int age;
     private Car car;

     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() {

     }
     public Person(String name, int age, Car car) {
         super();
         this.name = name;
         this.age = age;
         this.car = car;
     }

     @Override
     public String toString() {
         return "Person [name=" + name + ", age=" + age + ", car=" + car + "]";
     }

 }

 package me.spring.beans;

 public class HelloWorld {

     private String name;
     public void setName(String name) {
         this.name = name;
     }
     public void hello() {
         System.out.println("hello:" + name);
     }
 }

 package me.spring.beans;

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

 public class Main {

     public static void main(String[] args) {
 //        HelloWorld helloWorld = new HelloWorld();
 //        helloWorld.setName("Spring");
 //        helloWorld.hello();

         //1.创建Spring的IOC容器对象
         //ApplicationContext代表IOC容器
         //ClassPathXmlApplicationContext是ApplicationContext的实现类，该实现类从类路径下加载配置文件
         ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
         //2.从IOC容器中获取bean实例
         //利用id定位到IOC容器中的bean
         HelloWorld helloWorld = (HelloWorld) ctx.getBean("helloWorld");
         //利用类型返回IOC容器中的bean，担忧求IOC容器中只能有一个该类型的bean
         //HelloWorld helloWorld = ctx.getBean(HelloWorld.class);
         //3.调用hello方法
         helloWorld.hello();
         Car car = (Car) ctx.getBean("car");
         System.out.println(car);
         car = (Car) ctx.getBean("car2");
         System.out.println(car);
         Person person = (Person) ctx.getBean("person2");
         System.out.println(person);
     }

 }

(2)me.spring.beans.collections 测试集和属性

 package me.spring.beans.collections;

 import java.util.List;

 import me.spring.beans.Car;

 public class Person {

     private String name;
     private int age;

     private List<Car> cars;

     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 Person() {

     }

     public List<Car> getCars() {
         return cars;
     }

     public void setCars(List<Car> cars) {
         this.cars = cars;
     }

     public Person(String name, int age, List<Car> cars) {
         super();
         this.name = name;
         this.age = age;
         this.cars = cars;
     }

     @Override
     public String toString() {
         return "Person [name=" + name + ", age=" + age + ", cars=" + cars + "]";
     }
 }

 package me.spring.beans.collections;

 import java.util.Map;

 import me.spring.beans.Car;

 public class NewPerson {

     private String name;
     private int age;
     private Map<String, Car> cars;
     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 Map<String, Car> getCars() {
         return cars;
     }
     public void setCars(Map<String, Car> cars) {
         this.cars = cars;
     }

     public NewPerson() {
         // TODO Auto-generated constructor stub
     }
     public NewPerson(String name, int age, Map<String, Car> cars) {
         super();
         this.name = name;
         this.age = age;
         this.cars = cars;
     }
     @Override
     public String toString() {
         return "NewPerson [name=" + name + ", age=" + age + ", cars=" + cars + "]";
     }

 }

 package me.spring.beans.collections;

 import java.util.Properties;

 public class DataSource {

     private Properties properties;

     public Properties getProperties() {
         return properties;
     }

     public void setProperties(Properties properties) {
         this.properties = properties;
     }

     @Override
     public String toString() {
         return "DataSource [properties=" + properties + "]";
     }

 }
 package me.spring.beans.collections;

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

    public class Main {

        public static void main(String[] args) {
            ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
            Person person = (Person) ctx.getBean("person5");
            System.out.println(person);
            NewPerson newPerson = (NewPerson) ctx.getBean("newPerson");
            System.out.println(newPerson);
            DataSource dataSource = ctx.getBean(DataSource.class);
            System.out.println(dataSource.getProperties());
        }
    }