spring框架—-依赖注入之setter方法

大大源码 • 2023年4月24日 pm11:43 • 其他

setter注入

spring的DI（Dependency Injection）依赖注入有三种方式：
1.setter注入
2.构造器注入
3.接口注入
常用的时setter注入和构造器注入。setter注入又根据bean里的属性不同分成：对象注入、值注入（字面量注入）、集合注入、表达式注入、空值注入。

对象注入

1.Hello类

package cn.zgx.ioc;
public class Hello {
 public Hello(int i){
  
 }
public Hello(){
  System.out.println("hello co");
 }
 public void sayHello(){
  System.out.println("Hello World!!!");
 }

**tips：创建实体类时最好提供无参构造，且实现序列化的接口：Serializable

2.清单文件spring.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.xsd" >
     
  <!-- 告知spring框架用实例化哪些对象 -->
  <!-- id属性时对象在spring容器中的唯一标识，标识符可以带特殊符号  用name也可以 指定对象名，但不能带标识符 class属性时对象的类类型
   -->
 <bean id="hello" class="cn.zgx.ioc.Hello" >
 </bean>
 beans>

3.测试类

@Test
	public void test1(){
		//初始化spring容器
		AbstractApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring.xml");
		Hello hello=context.getBean("hello",Hello.class);
		hello.sayHello();
		context.close();
		
	}

输出结果：
hello co
Hello World!!!

值注入

1.ValueInject类

package cn.zgx.value;
public class ValueInject {
	private int age;
	private String address;
	public void setAge(int age) {
		this.age = age;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	@Override
	public String toString() {
		return "ValueInject [age=" + age + ", address=" + address + "]";
	}
	
}

2.清单文件spring_setter_value.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.xsd">
	<!-- 用清单文件告知spring框架对哪些类实例化对象 -->
	<!-- 
	  property节点告知spring做数据注入 ,对应setter方法
	 -->
	<bean id="valueInject"
	      class="cn.zgx.value.ValueInject">
		<property name="age" value="20"></property>      
	    <property name="address">
	        <value>北京</value>
	    </property>
	</bean>
</beans>

3.测试类

@Test
	public void test2(){
		//初始化spring容器
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_value.xml");
		ValueInject valueInject=context.getBean("valueInject",ValueInject.class);
		System.out.println(valueInject);
	}

输出结果：
ValueInject [age=20, address=北京]

集合注入

1.集合类Message

package cn.zgx.collection;

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

public class Message {
	private List list;
	private Set set;
	private Map map;
	private Properties props;
	public void setList(List list) {
		this.list = list;
	}
	public void setSet(Set set) {
		this.set = set;
	}
	public void setMap(Map map) {
		this.map = map;
	}
	public void setProps(Properties props) {
		this.props = props;
	}
	@Override
	public String toString() {
		return "Message [list=" + list + ", set=" + set + ", map=" + map + ", props=" + props + "]";
	}
	
	
}

2.清单文件spring_setter_collection.xml

集合注入分为直接集合注入和间接集合注入，但他们本质上区别不大。集合注入时如果在类中没有对集合做泛型限定，那么集合注入的值可以为任意类型，它也可以用value-ref来从spring容器取对象放进集合中注入。

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:util="http://www.springframework.org/schema/util" 
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop 
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx 
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/util 
        http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
	<!-- 用清单文件告知spring框架对哪些类实例化对象 -->
	<bean id="hello"
	      class="cn.zgx.ioc.Hello" />
	
	<!-- 直接集合注入 -->
	<bean id="message" 
	      class="cn.zgx.collection.Message">
		<property name="list">
			<list>
				<value>北京</value>
				<value>上海</value>
				<value>广州</value>
				<ref bean="hello"/>
			</list>
		</property>
		<property name="set">
			<set>
				<value>北京</value>
				<value>上海</value>
				<value>广州</value>
				<ref bean="hello"/>
			</set>
		</property>
		<property name="map">
			<map>
				<entry key="bj" value="北京"></entry>
				<entry key="sh" value="上海"></entry>
				<entry key="gz" value="广州"></entry>
				<entry key="h" value-ref="hello" ></entry>
			</map>
		</property>
		<property name="props">
			<props>
				<prop key="bj">北京</prop>
				<prop key="sh">上海</prop>
				<prop key="gz">广州</prop>
			</props>
		</property>      
	</bean>
	<!-- 间接集合 -->
	<!-- 集合的对象要交给spring容器来管理 -->
	<util:list id="uList">
		<value>北京</value>
		<value>上海</value>
		<value>广州</value>
		<ref bean="hello"/>
	</util:list>
	
	<util:map id="uMap">
		<entry key="bj" value="北京"></entry>
		<entry key="sh" value="上海"></entry>
		<entry key="gz" value="广州"></entry>
		<entry key="h" value-ref="hello" ></entry>
	</util:map>
	
	<util:set id="uSet">
		<value>北京</value>
		<value>上海</value>
		<value>广州</value>
		<ref bean="hello"/>
	</util:set>
	
	<util:properties id="uProps">
	    <prop key="bj">北京</prop>
		<prop key="sh">上海</prop>
		<prop key="gz">广州</prop>
	</util:properties>
	<bean id="message1"
          class="cn.zgx.collection.Message">
    	<property name="list" ref="uList"></property> 
    	<property name="set" ref="uSet"></property>     
        <property name="map" ref="uMap"></property>
        <property name="props" ref="uProps"></property>
    </bean>	
</beans>

3.测试类

@Test
	public void test3(){
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_collection.xml");
		Message message=context.getBean("message",Message.class);
		System.out.println(message);
	}
	@Test
	public void test4(){
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_collection.xml");
		Message message=context.getBean("message1",Message.class);
		System.out.println(message);
	}

test3输出结果：
Hello constructor()
Message [list=[北京, 上海, 广州, cn.zgx.ioc.Hello@4b1c1ea0], set=[北京, 上海, 广州, cn.zgx.ioc.Hello@4b1c1ea0], map={bj=北京, sh=上海, gz=广州, h=cn.zgx.ioc.Hello@4b1c1ea0}, props={bj=北京, sh=上海, gz=广州}]
test4输出结果：
Hello constructor()
Message [list=[北京, 上海, 广州, cn.zgx.ioc.Hello@4b1c1ea0], set=[北京, 上海, 广州, cn.zgx.ioc.Hello@4b1c1ea0], map={bj=北京, sh=上海, gz=广州, h=cn.zgx.ioc.Hello@4b1c1ea0}, props={bj=北京, sh=上海, gz=广州}]

表达式注入

表达式注入又分为两种：${}和#{}表达式，常用于读取属性文件的值

1.属性文件mysql.properties

jdbc_driverClass=com.mysql.jdbc.Driver
jdbc_url=jdbc:mysql://localhost:3306/tesdb
jdbc_userName=root
jdbc_userPassword=root

jdbc工具类：

package cn.zgx.expression;

import org.springframework.stereotype.Component;

@Component("jdbcutil")
public class JDBCUtil {
	private String driverClass;
	private String url;
	private String username;
	private String userpassword;
	public void setDriverClass(String driverClass) {
		this.driverClass = driverClass;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public void setUserpassword(String userpassword) {
		this.userpassword = userpassword;
	}
	@Override
	public String toString() {
		return "JDBCUtil [driverClass=" + driverClass + ", url=" + url + ", username=" + username + ", userpassword="
				+ userpassword + "]";
	}
	
}

2.清单文件

spring_setter_expression1.xml

${}方式

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:util="http://www.springframework.org/schema/util" 
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop 
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx 
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/util 
        http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
	<!-- 用清单文件告知spring框架对哪些类实例化对象 -->
	<!-- 属性注入   用$方式 
	 location属性可以放置多个属性文件,用逗号间隔,建议用类路径classpath取,
	  仅针对spring框架
	  把属性文件的数据加载到spring容器中-->
	<context:property-placeholder location="classpath:conf/mysql.properties"/>
	<bean id="jdbcUtil"
	      class="cn.zgx.expression.JDBCUtil">
		<property name="driverClass" value="${jdbc_driverClass}"></property>
		<property name="url" value="${jdbc_url}"></property>
		<property name="username" value="${jdbc_userName}"></property>
		<property name="userpassword" value="${jdbc_userPassword}"></property>      
	</bean>	
</beans>

spring_setter_expression2.xml

#{}方式
用此方式要给存到spring容器的属性文件一个id值，在根据这个id值取里面的数据

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:util="http://www.springframework.org/schema/util" 
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop 
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx 
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/util 
        http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
	<!-- 用清单文件告知spring框架对哪些类实例化对象 -->
	<!-- 属性注入  #{} 多个文件用逗号间隔 ,必须给一个id
	把属性文件的数据存储给spring容器,容器中以manyProperty,值是若干属性键值对
	-->
	<util:properties 
	   id="manyProperty"
	   location="classpath:conf/mysql.properties"></util:properties>
	<bean id="jdbcUtil"
	      class="cn.zgx.expression.JDBCUtil">
		<property name="driverClass" value="#{manyProperty.jdbc_driverClass}"></property>
		<property name="url" value="#{manyProperty.jdbc_url}"></property>
		<property name="username" value="#{manyProperty.jdbc_userName}"></property>
		<property name="userpassword" value="#{manyProperty.jdbc_userPassword}"></property>      
	</bean>	
</beans>

3.测试类

	@Test
	public void test5(){
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_expression1.xml");
		JDBCUtil jdbcUtil=context.getBean("jdbcUtil",JDBCUtil.class);
		System.out.println(jdbcUtil);
	}
	@Test
	public void test6(){
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_expression2.xml");
		JDBCUtil jdbcUtil=context.getBean("jdbcUtil",JDBCUtil.class);
		System.out.println(jdbcUtil);
	}

test5和test6都应输出：
JDBCUtil [driverClass=com.mysql.jdbc.Driver, url=jdbc:mysql://localhost:3306/tesdb, username=root, userpassword=root]

空值注入

1.kong类

package cn.zgx.kong;

public class Kong {
	private String str1;
	private String str2;
	public void setStr1(String str1) {
		this.str1 = str1;
	}
	public void setStr2(String str2) {
		this.str2 = str2;
	}
	@Override
	public String toString() {
		return "Kong [str1='" + str1 + "', str2=" + str2 + "]";
	}
	
}

2.清单文件spring_setter_kong.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:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:util="http://www.springframework.org/schema/util" 
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop 
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx 
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/util 
        http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
	<!-- 用清单文件告知spring框架对哪些类实例化对象 -->
	<bean id="kong"
	      class="cn.zgx.kong.Kong">
		<property name="str1" value=""></property>
		<property name="str2">
			<null></null>
		</property>
	</bean>
</beans>

3.测试类：

@Test
	public void test7(){
		//初始化spring容器
		ApplicationContext context =
				new ClassPathXmlApplicationContext("conf/spring_setter_kong.xml");
		Kong kong=context.getBean("kong",Kong.class);
		System.out.println(kong);
	}

输出结果：
Kong [str1=’’, str2=null]

总结：

1.setter方法常用的还是值注入和对象注入。对象注入是从spring容器中取出对应对象注入。setter方法要求bean节点的property属性名必须与该节点对应类中有匹配的setter方法，匹配规则是setter方法去掉set并将剩下的字符串首字母小写作为property属性名。比如，bean节点的class属性指向的类有一个setUsername，那么它对应的属性名应该为username。
2.空值注入是很鸡肋的写法。

<property name="str1" value=""></property>//相当于str1=""
<property name="str2">
<null></null>//相当于str2=null
</property>

原文链接：https://blog.csdn.net/weixin_42302727/article/details/102619090

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spring框架—-依赖注入之setter方法

setter注入

对象注入

1.Hello类

2.清单文件spring.xml

3.测试类

值注入

1.ValueInject类

2.清单文件spring_setter_value.xml

3.测试类

集合注入

1.集合类Message

2.清单文件spring_setter_collection.xml

3.测试类

表达式注入

1.属性文件mysql.properties

2.清单文件

spring_setter_expression1.xml

spring_setter_expression2.xml

3.测试类

空值注入

1.kong类

2.清单文件spring_setter_kong.xml

3.测试类：

总结：