spring基础应用（2）——依赖注入

依赖注入

当spring中一个对象A需要依赖另一个对象B的时候，我们需要在A里面引入一个B，同时需要给B注入一个对象，在这里我们先说的是手动装配，跟后面的自动装配autowired暂时没有关系。
通常手动装配一个对象我们有两种方法：

• 构造方法注入
• set方法注入

接下来我们依次来看，先看构造方法注入

构造方法注入

示例1：constructor-arg里面是ref

public class BeanOne {
    public BeanOne(BeanTwo beanTwo){
    }
}

<?xml version="1.0" encoding="UTF-8"?>


    
        
    
    
    
        
    

示例2：
当需要给基本数据类型和字符串注入的时候

public class ExampleBean {

    // Number of years to calculate the Ultimate Answer
    private final int years;

    // The Answer to Life, the Universe, and Everything
    private final String ultimateAnswer;

    public ExampleBean(int years, String ultimateAnswer) {
        this.years = years;
        this.ultimateAnswer = ultimateAnswer;
    }
}

//可以用type和value

    
    


//可以用index和value

    
    


//也可以用name和value

    
    

set方法注入

示例1：给普通类里面的属性赋值

public class ExampleBean {

    private AnotherBean beanOne;

    private YetAnotherBean beanTwo;

    private int i;

    public void setBeanOne(AnotherBean beanOne) {
        this.beanOne = beanOne;
    }

    public void setBeanTwo(YetAnotherBean beanTwo) {
        this.beanTwo = beanTwo;
    }

    public void setIntegerProperty(int i) {
        this.i = i;
    }
}

示例2：给内部类里面的属性赋值

public class Outer {
    private Person target;

    public void setTarget(Person target) {
        this.target = target;
    }

    public Person getTarget() {
        return target;
    }

    static class  Person{
        private String name;
        private String age;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getAge() {
            return age;
        }

        public void setAge(String age) {
            this.age = age;
        }
    }
}

示例3：为list、set、map、properties赋值

 
        
        
            
                administrator@example.org
                support@example.org
                development@example.org
            
        
        
        
            
                a list element followed by a reference
                
            
        
        
        
            
        
        
        
            
                just some string
                
            
        
    

package com.ali.testspring;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class TestMap {

    public List list1;
    public Set set1;
    public Map map1;
    public Properties properties1;

    public List getList1() {
        return list1;
    }

    public void setList1(List list1) {
        this.list1 = list1;
    }

    public Set getSet1() {
        return set1;
    }

    public void setSet1(Set set1) {
        this.set1 = set1;
    }

    public Map getMap1() {
        return map1;
    }

    public void setMap1(Map map1) {
        this.map1 = map1;
    }

    public Properties getProperties1() {
        return properties1;
    }

    public void setProperties1(Properties properties1) {
        this.properties1 = properties1;
    }
}

package com.ali.testspring;

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

public class Test {

    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("services.xml", "daos.xml");
        TestMap testMap=(TestMap)context.getBean("testMap");
        System.out.println(testMap.getList1().size());   //2
        System.out.println(testMap.getMap1().size());    //2
        System.out.println(testMap.getProperties1().size());    //3
        System.out.println(testMap.getSet1().size());   //2

    }
}