Spring框架入门之基于xml文件配置bean详解

妖狐艹你老母 2021-12-19 01:57 268阅读 0赞

## 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 ###

![复制代码][copycode.gif]

1 <?xml version="1.0" encoding="UTF-8"?>
      2 <beans xmlns="http://www.springframework.org/schema/beans"
      3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      4     xmlns:p="http://www.springframework.org/schema/p"
      5     xmlns:util="http://www.springframework.org/schema/util"
      6     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
      7         http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.1.xsd">
      8     
      9     
     14     
     15     <bean id="helloWorld" class="me.spring.beans.HelloWorld">
     16         <property name="name" value="Spring"></property>
     17     </bean>
     18     
     19     <bean id="car" class="me.spring.beans.Car">
     20         <constructor-arg value="Audi"></constructor-arg>
     21         <constructor-arg value="ShangHai"></constructor-arg>
     22         <constructor-arg value="300000"></constructor-arg>
     23     </bean>
     24 
     25     
     30     <bean id="car2" class="me.spring.beans.Car">
     31         <constructor-arg value="Baoma"></constructor-arg>
     32         <constructor-arg type="java.lang.String">
     33             <value><![CDATA[<Beijing>]]></value>
     34         </constructor-arg>
     35         <constructor-arg value="240" type="int"></constructor-arg>
     36     </bean>
     37     
     38     
     39     <bean id="person" class="me.spring.beans.Person">
     40         <property name="name" value="Tom"></property>
     41         <property name="age" value="24"></property>
     42         
     45          
     46         
     51         
     52         
     53         <property name="car">
     54             <bean class="me.spring.beans.Car">
     55                 <constructor-arg value="Ford"></constructor-arg>
     56                 <constructor-arg value="ChangAn"></constructor-arg>
     57                 <constructor-arg value="2354395" type="double"></constructor-arg>
     58             </bean>
     59         </property>
     60     </bean>
     61     
     62     <bean id="person2" class="me.spring.beans.Person">
     63         <constructor-arg value="Jerry"></constructor-arg>
     64         <constructor-arg value="25"></constructor-arg>
     65         <constructor-arg ref="car2"></constructor-arg>
     66 
     67         
     68         
     71         
     76         <property name="car.price" value="4546"></property>
     77     </bean>
     78     
     79     
     80     <bean id="person3" class="me.spring.beans.collections.Person">
     81         <property name="name" value="Mike"></property>
     82         <property name="age" value="34"></property>
     83         <property name="cars">
     84         
     85             <list>
     86                 <ref bean="car"/>
     87                 <ref bean="car2"/>
     88                 <bean class="me.spring.beans.Car">
     89                     <constructor-arg value="Ford"></constructor-arg>
     90                     <constructor-arg value="ChangAn"></constructor-arg>
     91                     <constructor-arg value="2354395" type="double"></constructor-arg>
     92                 </bean>
     93             </list>
     94         </property>
     95     </bean>
     96     <bean id="newPerson" class="me.spring.beans.collections.NewPerson">
     97         <property name="name" value="Rose"></property>
     98         <property name="age" value="23"></property>
     99         <property name="cars">
    100         
    101             <map>
    102                 <entry key="AA" value-ref="car"></entry>
    103                 <entry key="BB" value-ref="car2"></entry>
    104             </map>
    105         </property>
    106     </bean>
    107     
    108     
    109     <bean id="dataSource" class="me.spring.beans.collections.DataSource">
    110         <property name="properties">
    111         
    112             <props>
    113                 <prop key="user">root</prop>
    114                 <prop key="password">123456</prop>
    115                 <prop key="jdbcURL">jdbc:mysql://localhost:3306/test</prop>
    116                 <prop key="driverClass">com.mysql.jdbc.Driver</prop>
    117             </props>
    118         </property>
    119     </bean>
    120     
    121     
    122     <util:list id="cars">
    123         <ref bean="car"/>
    124         <ref bean="car2"/>
    125     </util:list>
    126     
    127     <bean id="person4" class="me.spring.beans.collections.Person">
    128         <property name="name" value="Jack"></property>
    129         <property name="age" value="34"></property>
    130         <property name="cars" ref="cars"></property>
    131     </bean>
    132     
    133     
    134     <bean id="person5" class="me.spring.beans.collections.Person" p:name="Queen" p:age="45" p:cars-ref="cars"></bean>
    135 </beans>

![复制代码][copycode.gif]

### 2.相关的实体类： ###

(1)me.spring.beans 包下：

![复制代码][copycode.gif]

1 package me.spring.beans;
      2 
      3 public class Car {
      4 
      5     private String brand;
      6     private String corp;
      7     private double price;
      8     private int maxSpeed;
      9     public Car(String brand, String corp, double price) {
     10         super();
     11         this.brand = brand;
     12         this.corp = corp;
     13         this.price = price;
     14     }
     15     
     16     public Car(String brand, String corp, int maxSpeed) {
     17         super();
     18         this.brand = brand;
     19         this.corp = corp;
     20         this.maxSpeed = maxSpeed;
     21     }
     22 
     23     public void setPrice(double price) {
     24         this.price = price;
     25     }
     26     
     27     public double getPrice() {
     28         return price;
     29     }
     30     @Override
     31     public String toString() {
     32         return "Car [brand=" + brand + ", corp=" + corp + ", price=" + price + ", maxSpeed=" + maxSpeed + "]";
     33     }
     34     
     35 }
     36 
     37 package me.spring.beans;
     38 
     39 public class Person {
     40 
     41     private String name;
     42     private int age;
     43     private Car car;
     44 
     45     public String getName() {
     46         return name;
     47     }
     48 
     49     public void setName(String name) {
     50         this.name = name;
     51     }
     52 
     53     public int getAge() {
     54         return age;
     55     }
     56 
     57     public void setAge(int age) {
     58         this.age = age;
     59     }
     60 
     61     public Car getCar() {
     62         return car;
     63     }
     64 
     65     public void setCar(Car car) {
     66         this.car = car;
     67     }
     68 
     69     public Person() {
     70         
     71     }
     72     public Person(String name, int age, Car car) {
     73         super();
     74         this.name = name;
     75         this.age = age;
     76         this.car = car;
     77     }
     78 
     79     @Override
     80     public String toString() {
     81         return "Person [name=" + name + ", age=" + age + ", car=" + car + "]";
     82     }
     83 
     84 }
     85 
     86 package me.spring.beans;
     87 
     88 public class HelloWorld {
     89 
     90     private String name;
     91     public void setName(String name) {
     92         this.name = name;
     93     }
     94     public void hello() {
     95         System.out.println("hello:" + name);
     96     }
     97 }
     98 
     99 package me.spring.beans;
    100 
    101 import org.springframework.context.ApplicationContext;
    102 import org.springframework.context.support.ClassPathXmlApplicationContext;
    103 
    104 public class Main {
    105 
    106     public static void main(String[] args) {
    107 //        HelloWorld helloWorld = new HelloWorld();
    108 //        helloWorld.setName("Spring");
    109 //        helloWorld.hello();
    110         
    111         //1.创建Spring的IOC容器对象
    112         //ApplicationContext代表IOC容器
    113         //ClassPathXmlApplicationContext是ApplicationContext的实现类，该实现类从类路径下加载配置文件
    114         ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    115         //2.从IOC容器中获取bean实例
    116         //利用id定位到IOC容器中的bean
    117         HelloWorld helloWorld = (HelloWorld) ctx.getBean("helloWorld");
    118         //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
    119         //HelloWorld helloWorld = ctx.getBean(HelloWorld.class);
    120         //3.调用hello方法
    121         helloWorld.hello();
    122         Car car = (Car) ctx.getBean("car");
    123         System.out.println(car);
    124         car = (Car) ctx.getBean("car2");
    125         System.out.println(car);
    126         Person person = (Person) ctx.getBean("person2");
    127         System.out.println(person);
    128     }
    129     
    130 }

![复制代码][copycode.gif]

**(2)me.spring.beans.collections 测试集和属性**

![复制代码][copycode.gif]

1 package me.spring.beans.collections;
      2 
      3 import java.util.List;
      4 
      5 import me.spring.beans.Car;
      6 
      7 public class Person {
      8 
      9     private String name;
     10     private int age;
     11     
     12     private List<Car> cars;
     13 
     14     public String getName() {
     15         return name;
     16     }
     17 
     18     public void setName(String name) {
     19         this.name = name;
     20     }
     21 
     22     public int getAge() {
     23         return age;
     24     }
     25 
     26     public void setAge(int age) {
     27         this.age = age;
     28     }
     29 
     30 
     31     public Person() {
     32         
     33     }
     34 
     35     public List<Car> getCars() {
     36         return cars;
     37     }
     38 
     39     public void setCars(List<Car> cars) {
     40         this.cars = cars;
     41     }
     42 
     43     public Person(String name, int age, List<Car> cars) {
     44         super();
     45         this.name = name;
     46         this.age = age;
     47         this.cars = cars;
     48     }
     49 
     50     @Override
     51     public String toString() {
     52         return "Person [name=" + name + ", age=" + age + ", cars=" + cars + "]";
     53     }
     54 }
     55 
     56 package me.spring.beans.collections;
     57 
     58 import java.util.Map;
     59 
     60 import me.spring.beans.Car;
     61 
     62 public class NewPerson {
     63 
     64     private String name;
     65     private int age;
     66     private Map<String, Car> cars;
     67     public String getName() {
     68         return name;
     69     }
     70     public void setName(String name) {
     71         this.name = name;
     72     }
     73     public int getAge() {
     74         return age;
     75     }
     76     public void setAge(int age) {
     77         this.age = age;
     78     }
     79     public Map<String, Car> getCars() {
     80         return cars;
     81     }
     82     public void setCars(Map<String, Car> cars) {
     83         this.cars = cars;
     84     }
     85     
     86     public NewPerson() {
     87         // TODO Auto-generated constructor stub
     88     }
     89     public NewPerson(String name, int age, Map<String, Car> cars) {
     90         super();
     91         this.name = name;
     92         this.age = age;
     93         this.cars = cars;
     94     }
     95     @Override
     96     public String toString() {
     97         return "NewPerson [name=" + name + ", age=" + age + ", cars=" + cars + "]";
     98     }
     99     
    100 }
    101 
    102 package me.spring.beans.collections;
    103 
    104 import java.util.Properties;
    105 
    106 public class DataSource {
    107 
    108     private Properties properties;
    109 
    110     public Properties getProperties() {
    111         return properties;
    112     }
    113 
    114     public void setProperties(Properties properties) {
    115         this.properties = properties;
    116     }
    117 
    118     @Override
    119     public String toString() {
    120         return "DataSource [properties=" + properties + "]";
    121     }
    122     
    123 }
    124 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());
            }
        }

[copycode.gif]: /images/20211219/b63ce3b0d465455bb9afe576b3c27a1f.png