【依赖注入】

╰半夏微凉° 2024-03-22 11:15 99阅读 0赞

### 构造器注入 ###

*  默认使用无参构造创建对象

package com.canso.pojo;
    
    public class Address {
        
        private String address;
    
        public Address() {
        
            System.out.println("Address无参构造器");
        }
    
        public String getAddress() {
        
            return address;
        }
    
        public void setAddress(String address) {
        
            this.address = address;
        }
    
        @Override
        public String toString() {
        
            return "Address{" +
                    "address='" + address + '\'' +
                    '}';
        }
    }

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
            Address address = (Address) context.getBean("address");
            System.out.println(address.toString());

*  假设我们要使用有参构造创建对象

1.下标赋值

<bean id="Address" class="com.canso.pojo.Address">
            <constructor-arg index="0" value="canso"/>
        </bean>

2.通过类型创建

<bean id="Address" class="com.canso.pojo.Address">
            <constructor-arg type="java.lang.String" value="canso"/>
        </bean>

3.直接参数名设置

<bean id="Address" class="com.canso.pojo.Address">
            <constructor-arg name="address" value="canso"/>
        </bean>

### set方式注入 ###

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
            https://www.springframework.org/schema/beans/spring-beans.xsd">
    
        <bean id="address" class="com.canso.pojo.Address"/>
    
        <bean id="Student" class="com.canso.pojo.Student">
    
            <property name="name" value="canso"/>
    
            <property name="address" ref="address"/>
    
            <property name="books">
                <array>
                    <value>红楼梦</value>
                    <value>西游记</value>
                    <value>水浒传</value>
                    <value>三国演义</value>
                </array>
            </property>
    
            <property name="hobbys">
                <list>
                    <value>篮球</value>
                    <value>音乐</value>
                    <value>跑步</value>
                </list>
            </property>
    
            <property name="card">
                <map>
                    <entry key="id" value="123456"/>
                    <entry key="sid" value="6789"/>
                </map>
            </property>
    
            <property name="games">
                <set>
                    <value>lol</value>
                    <value>qq</value>
                </set>
            </property>
    
            <property name="wife">
                <null/>
            </property>
    
            <property name="info">
                <props>
                    <prop key="学号">20200802</prop>
                    <prop key="姓名">小明</prop>
                    <prop key="性别">男</prop>
                </props>
            </property>
        </bean>
    </beans>

### p命名、c命名空间注入 ###

<?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:c="http://www.springframework.org/schema/c"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
            https://www.springframework.org/schema/beans/spring-beans.xsd">
    
        
        <bean id="address" class="com.canso.pojo.Address" p:address="canso"/>
        
        <bean id="address2" class="com.canso.pojo.Address" c:address="cs"/>
    </beans>

@Test
     public void test(){
        
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
            Object address = context.getBean("address2");
            System.out.println(address);
        }

注意点：p命名、c命名空间需要导入xml约束

xmlns:p="http://www.springframework.org/schema/p"
    xmlns:c="http://www.springframework.org/schema/c"