Spring03_DI

时间 2020-06-19

标签 spring03 spring 栏目 Spring 繁體版

原文原文链接

本教程源码请访问：tutorial_demojava

1、什么是依赖注入

依赖注入：Dependency Injection ，指容器负责建立和维护对象之间的依赖关系，而不是经过对象自己负责本身的建立和解决本身的依赖。在当前类须要用到其余类的对象，由Spring为咱们提供，咱们只须要在配置中说明。git

2、如何进行注入

2.一、构造函数注入

2.1.一、建立项目

在Idea中新建Maven工程；github

工程建立完成后添加相应的坐标。spring

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.codeaction</groupId>
    <artifactId>di</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.6.RELEASE</version>
        </dependency>
    </dependencies>
</project>

2.1.二、添加User类

package org.codeaction.bean;

import java.util.Date;

/**
 * 用户类
 */
public class User1 {
    private String name;
    private Integer age;
    private String address;
    private Date birthday;

    //有参构造方法
    public User(String name, Integer age, String address, Date birthday) {
        this.name = name;
        this.age = age;
        this.address = address;
        this.birthday = birthday;
    }


    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

User1类中必定要有有参的构造方法。apache

2.1.三、添加XML配置文件

XML文件在resource目录下。数组

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="now" class="java.util.Date"></bean>
    <bean id="user1" class="org.codeaction.bean.User1">
        <!-- 经过构造函数注入属性 -->
        <constructor-arg name="name" value="Tom"></constructor-arg>
        <constructor-arg name="age" value="10"></constructor-arg>
        <constructor-arg name="address" value="上海"></constructor-arg>
        <constructor-arg name="birthday" ref="now"></constructor-arg>
    </bean>
</beans>

构造函数注入使用constructor-arg标签，这个标签在bean标签的内部。maven

constructor-arg标签中的属性：ide

type：指定要注入的数据的数据类型，该数据类型也是构造函数中某个或某些参数的类型；
index：指定要注入的数据给构造函数中指定索引位置的参数赋值。索引的位置是从0开始；
name：指定给构造函数中指定名称的参数赋值；
value：提供基本类型和String类型的数据；
ref：指定其余的bean类型数据。它指的就是在spring的Ioc核心容器中出现过的bean对象。

前三个属性用于指定给构造函数中哪一个参数赋值，其中name属性最经常使用。函数

2.1.四、添加测试方法

package org.codeaction.test;

import org.codeaction.bean.User1;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

        User1 user1 = (User1) context.getBean("user1");
        System.out.println(user1);
    }
}

运行main方法，控制台输出以下：测试

User1{name='Tom', age=10, address='上海', birthday=Mon May 25 09:01:58 CST 2020}

2.二、set方法注入

2.2.一、添加User类

package org.codeaction.bean;

import java.util.Date;

public class User2 {
    private String name;
    private Integer age;
    private String address;
    private Date birthday;

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

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

    public void setAddress(String address) {
        this.address = address;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "User2{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

User2类中必定要有set方法。

2.2.二、修改XML配置文件

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="now" class="java.util.Date"></bean>
    <bean id="user1" class="org.codeaction.bean.User1">
        <!-- 经过构造函数注入属性 -->
        <constructor-arg name="name" value="Tom"></constructor-arg>
        <constructor-arg name="age" value="10"></constructor-arg>
        <constructor-arg name="address" value="上海"></constructor-arg>
        <constructor-arg name="birthday" ref="now"></constructor-arg>
    </bean>
	
    <bean id="user2" class="org.codeaction.bean.User2">
        <!-- 经过set方法注入 -->
        <property name="name" value="Bob"></property>
        <property name="age" value="20"></property>
        <property name="address" value="北京"></property>
        <property name="birthday" ref="now"></property>
    </bean>
</beans>

2.2.三、修改测试方法

package org.codeaction.test;

import org.codeaction.bean.User1;
import org.codeaction.bean.User2;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

		//User1 user1 = (User1) context.getBean("user1");
        //System.out.println(user1);

        User2 user2 = (User2) context.getBean("user2");
        System.out.println(user2);
    }
}

运行main方法，控制台输出以下：

User2{name='Bob', age=20, address='北京', birthday=Mon May 25 09:37:17 CST 2020}

2.三、注入复杂类型属性

本质上仍是给属性注入值，只是被注入的属性都是复杂类型（数组，List，Set，Map，Properties）。

2.3.一、添加User类

package org.codeaction.bean;

import java.util.*;

public class User3 {
    private String[] hobbies1;
    private List<String> hobbies2;
    private Set<String> hobbies3;
    private Map<String, String> idInfo1;
    private Properties idInfo2;

    public void setHobbies1(String[] hobbies1) {
        this.hobbies1 = hobbies1;
    }

    public void setHobbies2(List<String> hobbies2) {
        this.hobbies2 = hobbies2;
    }

    public void setHobbies3(Set<String> hobbies3) {
        this.hobbies3 = hobbies3;
    }

    public void setIdInfo1(Map<String, String> idInfo1) {
        this.idInfo1 = idInfo1;
    }

    public void setIdInfo2(Properties idInfo2) {
        this.idInfo2 = idInfo2;
    }

    public void show() {
        System.out.println("array----" + Arrays.toString(hobbies1));
        System.out.println("list----" + hobbies2);
        System.out.println("set----" + hobbies3);
        System.out.println("map----" + idInfo1);
        System.out.println("properties----" + idInfo2);
    }
}

2.3.二、修改XML配置文件

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="now" class="java.util.Date"></bean>
    <bean id="user1" class="org.codeaction.bean.User1">
        <!-- 经过构造函数注入属性 -->
        <constructor-arg name="name" value="Tom"></constructor-arg>
        <constructor-arg name="age" value="10"></constructor-arg>
        <constructor-arg name="address" value="上海"></constructor-arg>
        <constructor-arg name="birthday" ref="now"></constructor-arg>
    </bean>

    <bean id="user2" class="org.codeaction.bean.User2">
        <!-- 经过set方法注入 -->
        <property name="name" value="Bob"></property>
        <property name="age" value="20"></property>
        <property name="address" value="北京"></property>
        <property name="birthday" ref="now"></property>
    </bean>

    <!-- 注入复杂类型属性 -->
    <bean id="user3" class="org.codeaction.bean.User3">
        <!-- 注入复杂类型属性 -->
        <property name="hobbies1">
            <array>
                <value>篮球</value>
                <value>读书</value>
                <value>帆船</value>
            </array>
        </property>
        <property name="hobbies2">
            <list>
                <value>太极</value>
                <value>自由搏击</value>
                <value>咏春</value>
            </list>
        </property>
        <property name="hobbies3">
            <set>
                <value>旅游</value>
                <value>蹦极</value>
                <value>马拉松</value>
            </set>
        </property>
        <property name="idInfo1">
            <map>
                <entry key="name" value="John"></entry>
                <entry key="age">
                    <value>20</value>
                </entry>
                <entry key="gender" value="男"></entry>
            </map>
        </property>
        <property name="idInfo2">
            <props>
                <prop key="address">广州</prop>
                <prop key="height">180</prop>
            </props>
        </property>
    </bean>
</beans>

用于为List结构注入的标签：list、array、set；

用于为Map结构注入的标签：map、props；

结构相同，标签能够互换。

2.3.三、修改测试方法

package org.codeaction.test;

import org.codeaction.bean.User1;
import org.codeaction.bean.User2;
import org.codeaction.bean.User3;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

        //User1 user1 = (User1) context.getBean("user1");
        //System.out.println(user1);

        //User2 user2 = (User2) context.getBean("user2");
        //System.out.println(user2);

        User3 user3 = (User3)context.getBean("user3");
        user3.show();
    }
}

运行main方法，控制台输出以下：

array----[篮球, 读书, 帆船]
list----[太极, 自由搏击, 咏春]
set----[旅游, 蹦极, 马拉松]
map----{name=John, age=20, gender=男}
properties----{height=180, address=广州}

2.3.四、修改XML配置文件，互换标签

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="now" class="java.util.Date"></bean>
    <bean id="user1" class="org.codeaction.bean.User1">
        <!-- 经过构造函数注入属性 -->
        <constructor-arg name="name" value="Tom"></constructor-arg>
        <constructor-arg name="age" value="10"></constructor-arg>
        <constructor-arg name="address" value="上海"></constructor-arg>
        <constructor-arg name="birthday" ref="now"></constructor-arg>
    </bean>

    <bean id="user2" class="org.codeaction.bean.User2">
        <!-- 经过set方法注入 -->
        <property name="name" value="Bob"></property>
        <property name="age" value="20"></property>
        <property name="address" value="北京"></property>
        <property name="birthday" ref="now"></property>
    </bean>

    <!-- 注入复杂类型属性 -->
    <bean id="user3" class="org.codeaction.bean.User3">
        <!-- 注入复杂类型属性 -->
        <property name="hobbies1">
            <set>
                <value>旅游</value>
                <value>蹦极</value>
                <value>马拉松</value>
            </set>            
        </property>
        <property name="hobbies2">
            <array>
                <value>篮球</value>
                <value>读书</value>
                <value>帆船</value>
            </array>
        </property>
        <property name="hobbies3">
            <list>
                <value>太极</value>
                <value>自由搏击</value>
                <value>咏春</value>
            </list>
        </property>
        <property name="idInfo1">
            <props>
                <prop key="address">广州</prop>
                <prop key="height">180</prop>
            </props>
        </property>
        <property name="idInfo2">
            <map>
                <entry key="name" value="John"></entry>
                <entry key="age">
                    <value>20</value>
                </entry>
                <entry key="gender" value="男"></entry>
            </map>
        </property>
    </bean>
</beans>

运行main方法，控制台输出以下：

array----[旅游, 蹦极, 马拉松]
list----[篮球, 读书, 帆船]
set----[太极, 自由搏击, 咏春]
map----{height=180, address=广州}
properties----{age=20, name=John, gender=男}

经过上面的修改，说明标签结构相同，标签能够互换。

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