Spring--四种属性注入方式和复杂类型注入（数组、List、Map、prperties）详解

╰半橙微兮° 2021-08-13 16:27 435阅读 0赞

#### 第一种：set方法注入 ####

首先创建两个实体类 Car 和 User：

package pers.zhang.bean;
    
    public class Car { 
    	private String  name;
    	private String color;
    	
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    	public String getColor() { 
    		return color;
    	}
    	public void setColor(String color) { 
    		this.color = color;
    	}
    	@Override
    	public String toString() { 
    		return "Car [name=" + name + ", color=" + color + "]";
    	}
    }

package pers.zhang.bean;
    
    public class User { 
    	
    	private String name;
    	private Integer age;
    	private Car car;
    	
    	public Car getCar() { 
    		return car;
    	}
    	public void setCar(Car car) { 
    		this.car = car;
    	}
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    	public Integer getAge() { 
    		return age;
    	}
    	public void setAge(Integer age) { 
    		this.age = age;
    	}
    	@Override
    	public String toString() { 
    		return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    	}
    }

在applicationContext.xml中进行配置：

创建测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.User;
    
    public class Demo { 
    	@Test
    	public void fun1(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"user对象
    		User u = (User) ac.getBean("user");
    		//3 打印user对象
    		System.out.println(u);
    	}
    }

运行JUnit测试输出：

User [name=tom, age=18, car=Car [name=保时捷, color=红色]]

#### 第二种方式：构造函数注入 ####

首先，为User类添加3个构造函数：

package pers.zhang.bean;
    
    public class User { 
    	
    	private String name;
    	private Integer age;
    	private Car car;
    	
    	public User(String name, Car car) { 
    		System.out.println("User(String name, Car car)!!");
    		this.name = name;
    		this.car = car;
    	}
    	
    	public User(Car car,String name) { 
    		System.out.println("User(Car car,String name)!!");
    		this.name = name;
    		this.car = car;
    	}
    	
    	public User(Integer name, Car car) { 
    		System.out.println("User(Integer name, Car car)!!");
    		this.name = name+"";
    		this.car = car;
    	}
    	
    	public Car getCar() { 
    		return car;
    	}
    	public void setCar(Car car) { 
    		this.car = car;
    	}
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    	public Integer getAge() { 
    		return age;
    	}
    	public void setAge(Integer age) { 
    		this.age = age;
    	}
    	@Override
    	public String toString() { 
    		return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    	}
    }

applicationContext.xml配置：  
index：用于确定参数的位置  
type：用于确定参数的类型  
这两个属性可以完全确定一个构造函数。

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.User;
    
    public class Demo { 
    	@Test
    	public void fun2(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"user对象
    		User u = (User) ac.getBean("user2");
    		//3 打印user对象
    		System.out.println(u);
    		
    	}
    }

运行JUnit测试输出：

User(Integer name, Car car)!!
    User [name=24, age=null, car=Car [name=保时捷, color=红色]]

##### 第三种方式：P名称空间注入(Spring2.x版本后提供的方式) #####

其本质还是调空参构造，使用set方法注入。  
所以我们为User添加一个显式的空参构造：

package pers.zhang.bean;
    
    public class User { 
    	
    	private String name;
    	private Integer age;
    	private Car car;
    	
    	public User() { 
    		super();
    	}
    
    	public User(String name, Car car) { 
    		System.out.println("User(String name, Car car)!!");
    		this.name = name;
    		this.car = car;
    	}
    	
    	public User(Car car,String name) { 
    		System.out.println("User(Car car,String name)!!");
    		this.name = name;
    		this.car = car;
    	}
    	
    	public User(Integer name, Car car) { 
    		System.out.println("User(Integer name, Car car)!!");
    		this.name = name+"";
    		this.car = car;
    	}
    	
    	public Car getCar() { 
    		return car;
    	}
    	public void setCar(Car car) { 
    		this.car = car;
    	}
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    	public Integer getAge() { 
    		return age;
    	}
    	public void setAge(Integer age) { 
    		this.age = age;
    	}
    	@Override
    	public String toString() { 
    		return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    	}
    }

**一定记得引入p名称空间！**

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

applicationContext.xml配置：

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.User;
    
    public class Demo { 
    	@Test
    	public void fun3(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"user对象
    		User u = (User) ac.getBean("user3");
    		//3 打印user对象
    		System.out.println(u);
    		
    	}
    }

运行JUnit测试输出：

User [name=Jack, age=20, car=Car [name=保时捷, color=红色]]

#### 第四种方式：SpEL注入（Spring Expression Language）： ####

如果存在此种需求：取其他对象的属性值来创建新的对象，就可以使用SpEL。  
SpEL类似于EL表达式，格式为 \#\{ \}。  
需要注意的是，SpEL不支持引用类型注入。

applicationContext.xml配置：

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.User;
    
    public class Demo { 
    	@Test
    	public void fun4(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"user对象
    		User u = (User) ac.getBean("user4");
    		//3 打印user对象
    		System.out.println(u);
    		
    	}
    }

运行JUnit测试输出：

User [name=tom, age=18, car=Car [name=保时捷, color=红色]]

#### 复杂类型注入（数组、List、Map、prperties） ####

创建一个CollectionBean类：

package pers.zhang.bean;
    
    import java.util.Arrays;
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    
    public class CollectionBean { 
    	private Object[] arr;//数组类型注入
    	private List list;//list/set 类型注入
    	private Map map;//map类型注入
    	private Properties prop;//properties类型注入
    	
    	public Object[] getArr() { 
    		return arr;
    	}
    	public void setArr(Object[] arr) { 
    		this.arr = arr;
    	}
    	public List getList() { 
    		return list;
    	}
    	public void setList(List list) { 
    		this.list = list;
    	}
    	public Map getMap() { 
    		return map;
    	}
    	public void setMap(Map map) { 
    		this.map = map;
    	}
    	public Properties getProp() { 
    		return prop;
    	}
    	public void setProp(Properties prop) { 
    		this.prop = prop;
    	}
    	@Override
    	public String toString() { 
    		return "CollectionBean [arr=" + Arrays.toString(arr) + ", list=" + list + ", map=" + map + ", prop=" + prop
    				+ "]";
    	}
    }

*  **数组注入：**

1.  如果只向数组中注入一个值（对象），可以直接使用 value | ref 即可。

1.  如果向数组中注入多个值（对象）:

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd ">
    
        
    	<bean name="user" class="pers.zhang.bean.User" >
    		
    		<property name="name" value="tom" ></property>
    		<property name="age" value="18" ></property>
    		
    		<property name="car" ref="car" ></property>
    	</bean>
    
        <bean name="car" class="pers.zhang.bean.Car" >
    		<property name="name" value="保时捷" ></property>
    		<property name="color" value="红色" ></property>
    	</bean>
    
        
        <bean name="cb" class="pers.zhang.CollectionBean" >
            
            <property name="arr">
                
    		    <array>
    			    <value>tom</value>
    			    <value>jerry</value>
    			    <ref bean="user" />
    		    </array>
    	    </property>
        </bean>
    </beans>

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.CollectionBean;
    
    public class Demo { 
    	@Test
    	public void fun5(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"cb对象
    		CollectionBean cb = (CollectionBean) ac.getBean("cb");
    		//3 打印cb对象
    		System.out.println(cb);
    		
    	}
    }

运行JUnit测试输出：

CollectionBean [arr=[tom, jerry, User [name=tom, age=18, car=Car [name=保时捷, color=红色]]], 
                    list=null, 
                    map=null,
                    prop=null]

*  **List注入**  
    List与数组相似，如果只注入一个值（对象）使用value | ref 即可。此处不再举例。  
    注入多个值（对象）配置如下：

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.CollectionBean;
    
    public class Demo { 
    	@Test
    	public void fun5(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"cb对象
    		CollectionBean cb = (CollectionBean) ac.getBean("cb");
    		//3 打印cb对象
    		System.out.println(cb);
    		
    	}
    }

运行JUnit测试输出：

CollectionBean [arr=null, 
                    list=[jack, rose, User [name=tom, age=18, car=Car [name=保时捷, color=红色]]], 
                    map=null, 
                    prop=null]

*  **Map注入：**

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd ">
    
    
        
    	<bean name="user" class="pers.zhang.bean.User" >
    		
    		<property name="name" value="tom" ></property>
    		<property name="age" value="18" ></property>
    		
    		<property name="car" ref="car" ></property>
    	</bean>
    
          <bean name="user2" class="pers.zhang.bean.User" >
    		
    		<property name="name" value="Jerry" ></property>
    		<property name="age" value="10" ></property>
    		
    		<property name="car" ref="car" ></property>
    	</bean>
    
        <bean name="car" class="pers.zhang.bean.Car" >
    		<property name="name" value="保时捷" ></property>
    		<property name="color" value="红色" ></property>
    	</bean>
    
    
      
        <bean name="cb" class="pers.zhang.CollectionBean" >
           
    	    <property name="map" >
    		    <map>
    			    
    			    <entry key="url" value="jdbc:mysql:///crm" ></entry>
    			    
    			    <entry key="user" value-ref="user" ></entry>
    			    
    			    <entry key-ref="user2" value-ref="user2" ></entry>
    		    </map> 
    	    </property>
        </bean>
    
    </beans>

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.CollectionBean;
    
    public class Demo { 
    	@Test
    	public void fun5(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"cb对象
    		CollectionBean cb = (CollectionBean) ac.getBean("cb");
    		//3 打印cb对象
    		System.out.println(cb);
    		
    	}
    }

运行JUnit测试输出：

CollectionBean [arr=null,
                   list=null, 
                   map={ url=jdbc:mysql:///crm, 
                       user=User [name=tom, age=18, car=Car [name=保时捷, color=红色]], 
                        User [name=Jerry, age=10, car=Car [name=保时捷, color=红色]]=User [name=Jerry, age=10, car=Car [name=保时捷, color=红色]]}, 
                   prop=null]

*  **Property注入**

测试方法：

package pers.zhang.test;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import pers.zhang.bean.CollectionBean;
    
    public class Demo { 
    	@Test
    	public void fun5(){ 
    		
    		//1 创建容器对象
    		ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		//2 向容器"要"cb对象
    		CollectionBean cb = (CollectionBean) ac.getBean("cb");
    		//3 打印cb对象
    		System.out.println(cb);
    		
    	}
    }

运行JUnit测试输出：

CollectionBean [arr=null, 
                    list=null, 
                    map=null, 
                    prop={ driverClass=com.jdbc.mysql.Driver, password=1234, userName=root}]