Spring学习(五）

自动装备

1、定义

自动装配(autowiring): 将某个Bean实例中所引用的其它的Bean自动注入到当前Bean实例中
自动装配就是指由Spring来自动地注入依赖对象，无需人工参与。
自动装配的好处是减少构造器注入和setter注入配置，减少配置文件的长度。自动装配通过配置<bean>标签的 “autowire”属性来改变自动装配方式。

2、四种装配方式

no(default): 默认值，即不启动自动装配，需要显示地引用相应的bean

setter 注入 : ( setter-base )，提供setter方法进行注入,依赖于无参构造和setter方法

Person类

package ecut.ioc.autowiring;

public class Person {

    private Integer id;
    private String name;
    
    private Dog wangcai ;
    
    public Person() {
        super();
    }
    
    public Person(Dog wangcai) {
        super();
        this.wangcai = wangcai;
        System.out.println( "public Person(Dog)" );
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Dog getWangcai() {
        return wangcai;
    }

    public void setWangcai(Dog wangcai) {
        this.wangcai = wangcai;
    }

}

Dog类

package ecut.ioc.autowiring;

public class Dog {
    
    private String name ;

    public String getName() {
        return name;
    }

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

配置文件

<bean id="dog" class="ecut.ioc.autowiring.Dog" >
    <property name="name" value="拉的多不多" />
</bean>
        
<bean id="p" class="ecut.ioc.autowiring.Person" >
    <property name="id" value="1001" />
    <property name="name" value="华安" />
    <property name="wangcai" ref="dog" /> 
</bean>

构造方法注入 : ( constructor-base )通过构造方法往里面传入值

配置文件

<bean id="dog" class="ecut.ioc.autowiring.Dog" >
    <property name="name" value="拉的多不多" />
</bean>

<bean id="p" class="ecut.ioc.autowiring.Person" >
    <property name="id" value="1001" />
    <property name="name" value="华安" />
    <constructor-arg name="wangcai" ref="dog" /> 
</bean>

byName: 根据属性名称和被引用的bean名称来实现自动注入(setter)

byName-autowiring.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"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">


    <bean id="dog" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="拉的多不多" />
    </bean>

    <bean id="wangcai" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="旺财" />
    </bean>

    <!-- 根据 名称 实现 自动装配 ( setter ) -->
    <bean id="huaan" class="ecut.ioc.autowiring.Person"  autowire="byName" >
        <property name="id" value="1001" />
        <property name="name" value="华安" />
        <!-- <property name="wangcai" ref="wangcai" /> -->
    </bean>

</beans>

如果在被装配的bean中含有xxx属性(实际上是setter方法)，则会自动把id为xxx的bean装配上来
测试类

package ecut.ioc.autowiring;

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

public class AutowireByName {

    public static void main(String[] args) {
        
        String configLocations = "classpath:ecut/**/byName-autowiring.xml" ;
        
        AbstractApplicationContext container = new ClassPathXmlApplicationContext( configLocations );
        
        Person s = container.getBean( "huaan" , Person.class );
        
        System.out.println( s.getId() + " : " + s.getName() );
        
        Dog d = s.getWangcai();
        
        System.out.println( d.getName()  );
        
        container.close();
        
    }

}

byType: 根据属性类型和被引用的bean的类型来实现自动注入(setter)

byType-autowiring.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"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">


    <!--  NoUniqueBeanDefinitionException 
    <bean id="dog" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="拉的多不多" />
    </bean>
    -->
    
    <bean id="wangcai" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="旺财" />
    </bean>

    <!-- 根据 类型  实现 自动装配 ( setter ) -->
    <bean id="huaan" class="ecut.ioc.autowiring.Person"  autowire="byType" >
        <property name="id" value="1001" />
        <property name="name" value="华安" />
    </bean>

</beans>

如果在被装配的bean中含有一个xxx类型的属性，则会自动把类型为xxx的bean装配上来，但是如果含有多个xxx类型的bean，则抛出NoUniqueBeanDefinitionException
测试案例

package ecut.ioc.autowiring;

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

public class AutowireByType {

    public static void main(String[] args) {
        
        String configLocations = "classpath:ecut/**/byType-autowiring.xml" ;
        
        AbstractApplicationContext container = new ClassPathXmlApplicationContext( configLocations );
        
        Person s = container.getBean( "huaan" , Person.class );
        
        System.out.println( s.getId() + " : " + s.getName() );
        
        Dog d = s.getWangcai();
        
        System.out.println( d.getName()  );
        
        container.close();
        
    }

}

constructor: 根据构造方法的参数类型和被引用的Bean的类型实现自动装配(constructor)

当存在多个同种类型的Bean与构造方法中的参数类型相同时:
如果某Bean的名称跟参数的名称一致，则根据名称进行自动装配。constructor-autowiring.xml中bean的名称和构造方法中 public Person(Dog wangcai) 的参数保持一致。下面配置输出狗的名称是旺财

<?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 http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">


    <bean id="dog" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="拉的多不多" />
    </bean>
    
    <bean id="wangcai" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="旺财" />
    </bean>

    <!-- 根据 类型  实现 自动装配 ( constructor ) -->
    <bean id="huaan" class="ecut.ioc.autowiring.Person"  autowire="constructor" >
        <property name="id" value="1001" />
        <property name="name" value="华安" />
    </bean>

</beans>

如果这些Bean的名称跟参数的名称都不相同，则不再执行自动装配。但是，也不抛出异常

<?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 http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">


    <bean id="dog" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="拉的多不多" />
    </bean>
    
    <bean id="wc" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="旺财" />
    </bean>

    <!-- 根据 类型  实现 自动装配 ( constructor ) -->
    <bean id="huaan" class="ecut.ioc.autowiring.Person"  autowire="constructor" >
        <property name="id" value="1001" />
        <property name="name" value="华安" />
    </bean>

</beans>

当且仅当与构造方法中的参数类型相同的Bean只有一个时，此时根据类型进行自动装配。下面配置输出狗的名称是拉的多不多

<?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 http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">


    <bean id="dog" class="ecut.ioc.autowiring.Dog" >
        <property name="name" value="拉的多不多" />
    </bean>
    
    <!-- 根据 类型  实现 自动装配 ( constructor ) -->
    <bean id="huaan" class="ecut.ioc.autowiring.Person"  autowire="constructor" >
        <property name="id" value="1001" />
        <property name="name" value="华安" />
    </bean>

</beans>

测试类

package ecut.ioc.autowiring;

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

public class AutowireByConstructor {

    public static void main(String[] args) {
        
        String configLocations = "classpath:ecut/**/constructor-autowiring.xml" ;
        
        AbstractApplicationContext container = new ClassPathXmlApplicationContext( configLocations );
        
        Person s = container.getBean( "huaan" , Person.class );
        
        System.out.println( s.getId() + " : " + s.getName() );
        
        Dog d = s.getWangcai();
        
        System.out.println( d.getName()  );
        
        container.close();
        
    }

}

使用构造方法自动装备，创建person实例时，使用带参数的构造，并为参数注入指定类型的bean。

加载配置文件通配符

1、* 匹配同一级别路劲的多个字符，ecut/*/autowiring/constructor-autowiring.xml
2、 ** 匹配多级路劲中的多个字符，ecut/**/constructor-autowiring.xml

String configLocations = "classpath:ecut/**/constructor-autowiring.xml" ;
AbstractApplicationContext container = new ClassPathXmlApplicationContext( configLocations );

ecut.ioc.autowiring包中有一个constructor-autowiring.xml
3、 ?仅匹配一个字符

4、如果多个包中都beans.xml文件，并且期望全部加载它们，则可以写作classpath*:ecut/**/beans.xml

ecut包中有beans.xml， ecut.ex包中有beans.xml，ecut.xxx.yyyy包中有beans.xml

转载请于明显处标明出处

https://www.cnblogs.com/AmyZheng/p/9253193.html

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