Spring构造器的注入与配置bean的细节

àì夳堔傛蜴生んèń 2022-04-24 02:02 202阅读 0赞

**目录直通车**

1、 本文实验环境

2、 bean与bean之间相互访问

3、配置集合属性 List

4、 配置集合属性Map

5、 获取配置信息

6、 配置单例集合bean以供多个 bean 进行过引用

--------------------

**本文主要从bean的配置由繁到简。学习需要花费时间，这是笔者花费非常多的时间做出来的，静下心来阅读你会有大收获！有问题欢迎留言！**

## 1、 本文实验环境 ##

文件目录

![2019041117114561.png][]

**首先新建一个 TestConstructor 的bean。**

public class TestConstructor {
        /**
         * 一个汽车的例子
         */
        private String brand;
        private String province;
        private double price;
        private int maxSpeed;
    
        public TestConstructor(String brand, String province, double price) {
            super();
            this.brand = brand;
            this.province = province;
            this.price = price;
        }
    
        public TestConstructor(String brand, double price, int maxSpeed) {
            super();
            this.brand = brand;
            this.price = price;
            this.maxSpeed = maxSpeed;
        }
    
        @Override
        public String toString() {
            return "TestConstructor{" +
                    "brand='" + brand + '\'' +
                    ", province='" + province + '\'' +
                    ", price=" + price +
                    ", maxSpeed=" + maxSpeed +
                    '}';
        }
    
    
    }

**在 constructorContext.xml 中添加以下代码对构造器注入**

<bean id="testConstructor1" class="com.spring.beans.ConstructorInject.TestConstructor">
            <constructor-arg name="brand" value="Audi"> </constructor-arg>
            <constructor-arg name="province" value="Beijing"> </constructor-arg>
            <constructor-arg name="price" value="300000" type="double"> </constructor-arg>
        </bean>
        
        <bean id="testConstructor2" class="com.spring.beans.ConstructorInject.TestConstructor">
            <constructor-arg name="brand" value="BaoMa" type="java.lang.String"> </constructor-arg>
            <constructor-arg name="price" value="300000" type="double"> </constructor-arg>
            <constructor-arg name="maxSpeed" value="200" type="int"> </constructor-arg>
        </bean>

## 2、 bean与bean之间相互访问 ##

**新建一个名为Person的 bean**

public class Person {
        private String name;
        private int age;
        private TestConstructor car;
    
        public Person() {
        }
    
        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 TestConstructor getCar() {
            return car;
        }
    
        public void setCar(TestConstructor car) {
            this.car = car;
        }
    
        @Override
        public String toString() {
            return "Person{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", car=" + car +
                    '}';
        }
    }

组成应用程序的Bean 经常需要相互协作来完成应用程序的功能，所以要使得Bean能够相互访问，就必须在配置文件中指定对Bean的应用。通过ref元素为bean的属性或构造器参数指定对Bean的引用。有以下三种写法:

1）

2）

3）内部bean(可给bean赋值),但不能用外部bean使用，只能内部使用。

## 3、配置集合属性 List ##

新建一个名为PersonList的bean

import java.util.List;
    
    public class PersonList {
        private String name;
        private int age ;
    
        private List<TestConstructor> car;
    
        public PersonList() {
        }
    
        @Override
        public String toString() {
            return "PersonList{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", 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 List<TestConstructor> getCar() {
            return car;
        }
    
        public void setCar(List<TestConstructor> car) {
            this.car = car;
        }
    }

在xml文件中配置上面刚刚添加的这个bean。

在Application执行类中添加代码

得到以下结果

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNjQ3OTk5_size_16_color_FFFFFF_t_70][]

##  4、 配置集合属性Map ##

新建一个PersonMap

import java.util.Map;
    
    public class PersonMap {
        private  String name;
        private  int age ;
        private Map<String,TestConstructor> car;
    
        public PersonMap() {
        }
    
        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, TestConstructor> getCar() {
            return car;
        }
    
        public void setCar(Map<String, TestConstructor> car) {
            this.car = car;
        }
    
        @Override
        public String toString() {
            return "PersonMap{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", car=" + car +
                    '}';
        }
    }

xml 添加如下代码配置bean

<bean id="personMap" class="com.spring.beans.ConstructorInject.PersonMap">
            <property name="name" value="DJun"> </property>
            <property name="age" value="22"> </property>
            <property name="car">
                <map>
                    <entry key="AA" value-ref="testConstructor1"> </entry>
                    <entry key="BB" value-ref="testConstructor2"> </entry>
                </map>
            </property>
        </bean>

在Application中添加

PersonMap personMap = (PersonMap) applicationContext.getBean("personMap");
            System.out.println("----- PersonMap ------\n"+personMap);

## 5、 获取配置信息 ##

新建DataSource的bean

import java.util.Properties;
    
    public class DataSource {
        private Properties properties;
    
        public Properties getProperties() {
            return properties;
        }
    
        public void setProperties(Properties properties) {
            this.properties = properties;
        }
    
        public DataSource() {
        }
    
        @Override
        public String toString() {
            return "DataSource{" +
                    "properties=" + properties +
                    '}';
        }
    }

<bean id="dataSource" class="com.spring.beans.ConstructorInject.DataSource">
           <property name="properties">
               <props>
                   <prop key="username">root</prop>
                   <prop key="password">root</prop>
                   <prop key="jdbcUrl"> jdbc:mysql://test</prop>
                   <prop key="driverClass">com.mysql.jdbc.Driver</prop>
               </props>
           </property>
        </bean>

![20190411173924600.png][]

## 6、 配置单例集合bean以供多个 bean 进行过引用 ##

其实运行完了上面的实例之后，发现每次都在使用testConstructor1和testConstructor2，单个bean使用的话，还没有多大的感觉。但是如果像我上面那样去写就非常的臃肿。

请看下面这个解决方案：

在xml中添加以下内容

<util:list id="cars">
            <ref bean="testConstructor1"/>
            <ref bean="testConstructor2"/>
        </util:list>
        <bean id="singleList" class="com.spring.beans.ConstructorInject.PersonList">
            <property name="name" value="DJun"/>
            <property name="age" value="22"/>
            <property name="car" ref="cars"/>
        </bean>
        
        <bean id="personP" class="com.spring.beans.ConstructorInject.Person"
              p:name="DJun"
              p:age="22"
              p:car-ref="testConstructor1"/>

完整的Application代码：

import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class Application {
        public static void main(String[] args) {
            ApplicationContext applicationContext =new ClassPathXmlApplicationContext("com/spring/beans/ConstructorInject/ConstructorContext.xml");
            Person person = (Person)applicationContext.getBean("person");
            System.out.println("----- Person ------\n"+person);
    
            PersonList personList = (PersonList) applicationContext.getBean("personList");
            System.out.println("----- PersonList ------\n"+personList);
    
            PersonMap personMap = (PersonMap) applicationContext.getBean("personMap");
            System.out.println("----- PersonMap ------\n"+personMap);
    
            DataSource dataSource = (DataSource) applicationContext.getBean("dataSource");
            System.out.println("---------DataSource ----------\n "+dataSource);
    
            PersonList personList1 = (PersonList) applicationContext.getBean("singleList");
            System.out.println("------- PersonList -------\n" + personList1);
    
            Person personP = (Person) applicationContext.getBean("personP");
            System.out.println("------- personP -------\n" + personP);
        }
    }

完整的xml配置代码：

<?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:util="http://www.springframework.org/schema/util"
           xmlns:p="http://www.springframework.org/schema/p"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
    
        
        <bean id="testConstructor1" class="com.spring.beans.ConstructorInject.TestConstructor">
            <constructor-arg name="brand" value="Audi"> </constructor-arg>
            <constructor-arg name="province" value="Beijing"> </constructor-arg>
            <constructor-arg name="price" value="300000" type="double"> </constructor-arg>
        </bean>
        
        <bean id="testConstructor2" class="com.spring.beans.ConstructorInject.TestConstructor">
            <constructor-arg name="brand" value="BaoMa" type="java.lang.String"> </constructor-arg>
            <constructor-arg name="price" value="300000" type="double"> </constructor-arg>
            <constructor-arg name="maxSpeed" value="200" type="int"> </constructor-arg>
        </bean>
        
        <bean id="person" class="com.spring.beans.ConstructorInject.Person">
            <property name="name" value="DJun"> </property>
            <property name="age" value="22"> </property>
            
            
            
            
            
                
            
            
            <property name="car">
                <bean class="com.spring.beans.ConstructorInject.TestConstructor">
                    <constructor-arg name="brand" value="Ford"> </constructor-arg>
                    <constructor-arg name="price" value="200000"> </constructor-arg>
                    <constructor-arg name="maxSpeed" value="200"> </constructor-arg>
                </bean>
                
                
            </property>
            
            
        </bean>
        
        <bean id="personList" class="com.spring.beans.ConstructorInject.PersonList">
            <property name="name" value="DJun"> </property>
            <property name="age" value="22"> </property>
            <property name="car">
                <list>
                    <ref bean="testConstructor2"/>
                    <ref bean="testConstructor1"/>
                </list>
            </property>
        </bean>
    
        
        <bean id="personMap" class="com.spring.beans.ConstructorInject.PersonMap">
            <property name="name" value="DJun"> </property>
            <property name="age" value="22"> </property>
            <property name="car">
                <map>
                    <entry key="AA" value-ref="testConstructor1"> </entry>
                    <entry key="BB" value-ref="testConstructor2"> </entry>
                </map>
            </property>
        </bean>
        
        <bean id="dataSource" class="com.spring.beans.ConstructorInject.DataSource">
           <property name="properties">
               <props>
                   <prop key="username">root</prop>
                   <prop key="password">root</prop>
                   <prop key="jdbcUrl"> jdbc:mysql://test</prop>
                   <prop key="driverClass">com.mysql.jdbc.Driver</prop>
               </props>
           </property>
        </bean>
        
        <util:list id="cars">
            <ref bean="testConstructor1"/>
            <ref bean="testConstructor2"/>
        </util:list>
        <bean id="singleList" class="com.spring.beans.ConstructorInject.PersonList">
            <property name="name" value="DJun"/>
            <property name="age" value="22"/>
            <property name="car" ref="cars"/>
        </bean>
        
        <bean id="personP" class="com.spring.beans.ConstructorInject.Person"
              p:name="DJun"
              p:age="22"
              p:car-ref="testConstructor1"/>
    
    </beans>

[2019041117114561.png]: /images/20220221/6ddd60a7ccef455198a430933ad624c2.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNjQ3OTk5_size_16_color_FFFFFF_t_70]: /images/20220221/498738b0916c490195fd66884d55276b.png
[20190411173924600.png]: /images/20220221/c52cc23f7b424ca5b37fcec8ee94cf8c.png