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Spring的依赖注入方法

由 落花浮王杯 提交于 2019-12-26 10:09:10

文章目录

Spring中依赖注入的方法

基于构造方法的注入

基于构造方法的注入：可以带参，也可以不带参，以下展示的是带参的
首先新建一个StudentConstructor类，里面带有一个带参的构造方法

package com.zhbit.pojo;

public class StudentConstructor {
    private String name;
    private String sex;
    private String studentNo;
    private int age;
    
    public StudentConstructor(String name, String sex, String studentNo, int age) {
        this.name = name;
        this.sex = sex;
        this.studentNo = studentNo;
        this.age = age;
    }

    @Override
    public String toString() {
        return "StudentConstructor{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", studentNo='" + studentNo + '\'' +
                ", age=" + age +
                '}';
    }
}

spring的构造器注入方法主要分为三种：1.根据索引赋值，索引都是以0开始 2.根据参数的名字传值 3.根据所属类型传值
下面对这三种方法进行简单分析。

根据索引赋值

配置constructor-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">
    <!--采用构造器的index-value方式注入 -->
    <bean id="studentConstructor" class="com.zhbit.pojo.StudentConstructor">
        <constructor-arg index="0" value="小明"/>
        <constructor-arg index="1" value="男"/>
        <constructor-arg index="2" value="S001"/>
        <constructor-arg index="3" value="23"/>
    </bean>

</beans>

编写测试类MyConstructorBeanTest.class

import com.zhbit.pojo.StudentConstructor;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyConstructorBeanTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("constructor-beans.xml");
        StudentConstructor StudentConstructor = (StudentConstructor) context.getBean("studentConstructor");
        System.out.println(StudentConstructor);

    }
}

测试结果：
注入成功

根据所属类型传值

配置constructor-beans.xml

<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">
    <!--&lt;!&ndash;采用构造器的index-value方式注入 &ndash;&gt;
    <bean id="studentConstructor" class="com.zhbit.pojo.StudentConstructor">
        <constructor-arg index="0" value="小明"/>
        <constructor-arg index="1" value="男"/>
        <constructor-arg index="2" value="S001"/>
        <constructor-arg index="3" value="23"/>
    </bean>-->
    <!-- 使用构造器的name-value方式注入 该办法通过反射实现注入-->
    <bean id="studentConstructor" class="com.zhbit.pojo.StudentConstructor">
        <constructor-arg name="name" value="小红"/>
        <constructor-arg name="age" value="18"/>
        <constructor-arg name="sex" value="女"/>
        <constructor-arg name="studentNo" value="160202103483"/>
    </bean>
</beans>

编写测试类MyConstructorBeanTest.class

import com.zhbit.pojo.StudentConstructor;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyConstructorBeanTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("constructor-beans.xml");
        StudentConstructor StudentConstructor = (StudentConstructor) context.getBean("studentConstructor");
        System.out.println(StudentConstructor);

    }
}

测试结果
注入成功

根据所属类型传值(不推荐)

不推荐的原因：一个类可以有好几个相同基本类型的变量，这样会混淆，这里就不做详细说明了。

基于setter注入

编写StudentSetter.class

package com.zhbit.pojo;

public class StudentSetter {
    private String name;
    private String sex;
    private String studentNo;
    private int age;

    public String getName() {
        return name;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getStudentNo() {
        return studentNo;
    }

    public void setStudentNo(String studentNo) {
        this.studentNo = studentNo;
    }

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "StudentSetter{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", studentNo='" + studentNo + '\'' +
                ", age=" + age +
                '}';
    }
}

这里面的每一个属性的set方法必须有，没有的话会在xml文件里面报错

接下来就是setter-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">
    <!--通过setter方法注入属性-->
    <bean id="studentSetter" class="com.zhbit.pojo.StudentSetter"  >
        <property name="name" value="小橙"/>
        <property name="age"  value="18"/>
        <property name="sex"  value="男"/>
        <property name="studentNo" value="123"/>
    </bean>

</beans>

编写测试类

import com.zhbit.pojo.StudentSetter;
import com.zhbit.pojo.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MySetterTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("setter-beans.xml");
        StudentSetter studentSetter = (StudentSetter) context.getBean("studentSetter");
        System.out.println(studentSetter);
    }
}

测试结果：
注入成功

基于接口的注入(不常用，这里不说明了)

拓展方式注入

P命名空间注入(基于setter方法注入)

编写UserP.class类

package com.zhbit.pojo;

public class UserP {
    private String name;
    private int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
	 @Override
    public String toString() {
        return "UserP{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

编写userPBeans.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"
       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-->
    <bean id="userP" class="com.zhbit.pojo.UserP" p:name="小明" p:age="18">

    </bean>
</beans>

其中

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

是用来导入P-namespace命令
编写测试类MyUserPTest.class

import com.zhbit.pojo.UserP;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyUserPTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("userPBeans.xml");
        UserP userP = context.getBean("userP",UserP.class);
        System.out.println(userP.toString());
    }
}

测试结果：
P命名空间注入成功

C命名空间注入(基于控制器注入)

编写UserC.class

package com.zhbit.pojo;

public class UserC {
    private String name;
    private int age;

    public UserC() {
    }

    public UserC(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

编写userCBeans.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:c="http://www.springframework.org/schema/c"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!--c命名空间注入，通过构造器注入:constructor-arg -->
    <bean id="userC" class="com.zhbit.pojo.UserC" c:age="18" c:name="拼命三郎"/>
</beans>

其中

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

为C命名空间的导入
编写测试类MyUserCTest.class

import com.zhbit.pojo.UserC;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyUserCTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("userCBeans.xml");
        UserC userC = context.getBean("userC", UserC.class);
        System.out.println(userC.toString());
    }

}

测试结果：
C命名空间注入成功
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，可以到spring官网查找

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