依赖注入
目录
DI(Dependence Injection)依赖注入
1. 构造器注入
有无参构造器:property
用有参构造器:constructor-arg,三种方式
2. Set方式注入
1. 依赖注入: Set注入
- 依赖: bean对象的创建依赖于容器!
- 注入: bean对象中的所有属性,由容器来注入!
2. 环境搭建
1. 复杂类型
package com.wang.pojo;
public class Address {
private String address;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Address{" +
"address='" + address + '\'' +
'}';
}
}
2. 真实测试对象
package com.wang.pojo;
import java.util.*;
public class Student {
private String name;
private Address address;
private String[] book;
private List<String> hobbies;
private Map<String,String> card;
private Set<String> games;
private String wife;
private Properties info;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public String[] getBook() {
return book;
}
public void setBook(String[] book) {
this.book = book;
}
public List<String> getHobbies() {
return hobbies;
}
public void setHobbies(List<String> hobbies) {
this.hobbies = hobbies;
}
public Map<String,String> getCard() {
return card;
}
public void setCard(Map<String,String> card) {
this.card = card;
}
public Set<String> getGames() {
return games;
}
public void setGames(Set<String> games) {
this.games = games;
}
public String getWife() {
return wife;
}
public void setWife(String wife) {
this.wife = wife;
}
public Properties getInfo() {
return info;
}
public void setInfo(Properties info) {
this.info = info;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
",address=" + address +
",book=" + Arrays.toString(book) +
",hobbies=" + hobbies +
",card=" + card +
",games=" + games +
",wife='" + wife + '\'' +
",info=" + info +
'}';
}
}
3. beans.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">
<bean id="address" class="com.wang.pojo.Address">
<property name="address" value="南京"/>
</bean>
<bean id="student" class="com.wang.pojo.Student">
<!--第一种,普通值注入(基本类型),value-->
<property name="name" value="wang sky"/>
<!--第二种,Bean注入(自定义类型),ref,传入的值在xml中对应的id的bean中指定,不指定则为null-->
<property name="address" ref="address"/>
<!--数组注入-->
<property name="book">
<array>
<value>红楼梦</value>
<value>西游记</value>
<value>水浒传</value>
<value>三国演义</value>
</array>
</property>
<!--list注入-->
<property name="hobbies">
<list>
<value>听音乐</value>
<value>看电影</value>
<value>打电动</value>
</list>
</property>
<!--Map注入-->
<property name="card">
<map>
<entry key="身份证" value="11111122222222333333"/>
<entry key="银行卡" value="123456871313545343513"/>
</map>
</property>
<!--Set注入-->
<property name="games">
<set>
<value>WOW</value>
<value>M&B2</value>
<value>FF14</value>
</set>
</property>
<!--空值注入-->
<!-- <property name="wife" value=""/>-->
<!--Null注入-->
<property name="wife">
<null/>
</property>
<!--properties注入(K-V对)-->
<property name="info">
<props>
<prop key="学号">20201123</prop>
<prop key="性别">男性</prop>
<prop key="别名">小明</prop>
</props>
</property>
</bean>
</beans>
4. 测试类
import com.wang.pojo.Student;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MyTest {
@Test
public void SpringTest() {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student.toString());
}
}
3. 拓展方式注入
我们可以使用P命名空间和C命名空间进行注入
1. beans.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:p="http://www.springframework.org/schema/p"
xmlns:c="http://www.springframework.org/schema/c"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!--P命名空间注入,可以直接注入属性的值: property,要先在上面导入xmlns:p="http://www.springframework.org/schema/p"-->
<bean id="user" class="com.wang.pojo.User" p:name="wang sky" p:age="18"/>
<!--C命名空间注入,可以通过构造器注入: constructor,但要求bean中有构造器! 要先在上面导入xmlns:c="http://www.springframework.org/schema/c"-->
<bean id="user2" class="com.wang.pojo.User" c:age="18" c:name="wang sky"/>
</beans>
2. 测试
@Test
public void SpringTest2() {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("userbeans.xml");
//可以向getBean的第二个参数利用反射传入User的类型,这样就不用再进行类型转换
User user = context.getBean("user",User.class);
System.out.println(user.toString());
}
@Test
public void SpringTest3() {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("userbeans.xml");
//可以向getBean的第二个参数利用反射传入User的类型,这样就不用再进行类型转换
User user = context.getBean("user2",User.class);
System.out.println(user.toString());
}
3. 注意点
P命名和C命名空间不能直接使用,需要导入xml约束
xmlns:p="http://www.springframework.org/schema/p"
xmlns:c="http://www.springframework.org/schema/c"
