spring4.x依赖注入方法(DI)

分手后的思念是犯贱 2022-06-08 05:08 164阅读 0赞

1.DI方法

属性注入(Setter方法注入)  
构造器注入  
工厂方法注入（很少使用，不推荐）

2.属性注入(Setter方法注入)

applicationContext-bean.xml

<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
    
    
            <bean id="OutputHelper" class="cn.com.pojo.OutputHelper">
                <property name="outputGenerator">
                    <ref bean="CsvOutputGenerator" />
                </property>
            </bean>
    
        <bean id="CsvOutputGenerator" class="cn.com.pojo.CsvOutputGenerator" />
        <bean id="JsonOutputGenerator" class="cn.com.pojo.JsonOutputGenerator" />
    
        </beans>

OutputHelper.java

package cn.com.pojo.output;
    
    import com.yiibai.output.IOutputGenerator;
    
    public class OutputHelper { 
        IOutputGenerator outputGenerator;
    
        public void setOutputGenerator(IOutputGenerator outputGenerator){
            this.outputGenerator = outputGenerator;
        }
    
    }

调用方法Main.java

package cn.com.pojo;
    
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class Main {
    
        public static void main(String[] args) {
    
            //1. 创建 Spring 的 IOC 容器
            ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext-bean.xml");
    
            //2. 从 IOC 容器中获取 bean 的实例
            OutputHelper outputHelper = (OutputHelper) ctx.getBean("OutputHelper");
    
            //根据类型来获取 bean 的实例: 要求在 IOC 容器中只有一个与之类型匹配的 bean, 若有多个则会抛出异常. 
            //一般情况下, 该方法可用, 因为一般情况下, 在一个 IOC 容器中一个类型对应的 bean 也只有一个. 
            // OutputHelper outputHelper = ctx.getBean(OutputHelper.class);
    
            //3. 使用 bean
            System.out.println(outputHelper)
        }   
    }

3.构造器注入  
applicationContext-bean..xml

<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
    
    
        <bean id="CustomerBean" class="cn.com.pojo.Customer">
        
            <constructor-arg type="java.lang.String">
                <value>yiibai</value>
            </constructor-arg>
    
            <constructor-arg type="java.lang.String">
                <value>188</value>
            </constructor-arg>
    
            <constructor-arg type="int">
                <value>28</value>
            </constructor-arg>
    
        </bean>
    
    </beans>

Customer.java

package cn.com.pojo;
    
    public class Customer 
    {
        private String name;
        private String address;
        private int age;
    
        public Customer(String name, String address, int age) {
            this.name = name;
            this.address = address;
            this.age = age;
        }
    
        public Customer(String name, int age, String address) {
            this.name = name;
            this.age = age;
            this.address = address;
        }
        //getter and setter methods
        public String toString(){
            return " name : " +name + "\n address : "
                   + address + "\n age : " + age;
        }
    
    }

运行类：App .java

package cn.com.pojo;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class App { 
        public static void main( String[] args )
        {
            ApplicationContext context = 
              new ClassPathXmlApplicationContext(new String[] {
       "Spring-Customer.xml"});
    
            Customer cust = (Customer)context.getBean("CustomerBean");
            System.out.println(cust);
            // name : yiibai
            // address : 28
            // age : 188
        }
    }

4工厂方法注入（很少使用，不推荐）