spring——Spring 注入内部Bean——setter 方式注入内部 Bean

港控/mmm° 2024-03-31 17:23 90阅读 0赞

我们将定义在 <bean> 元素的 <property> 或 <constructor-arg> 元素内部的 Bean，称为“内部 Bean”。

项目依赖：

<?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.example</groupId>
        <artifactId>ssw</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <properties>
            <maven.compiler.source>8</maven.compiler.source>
            <maven.compiler.target>8</maven.compiler.target>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>5.3.6</version>
            </dependency>
        </dependencies>
    
    </project>

![fb5a3d6bde1db13313284ced04f340dd.png][]

dept类：

package org.example;
    
    public class Dept {
        //部门编号
        private String deptNo;
        //部门名称
        private String deptName;
    
        public void setDeptNo(String deptNo) {
            this.deptNo = deptNo;
        }
    
        public void setDeptName(String deptName) {
            this.deptName = deptName;
        }
    
        @Override
        public String toString() {
            return "Dept{" +
                    "deptNo='" + deptNo + '\'' +
                    ", deptName='" + deptName + '\'' +
                    '}';
        }
    }

![f4da531471a28a6a51346e53cca0c643.png][]

employee类：

package org.example;
    
    public class Employee {
        //员工编号
        private String empNo;
        //员工姓名
        private String empName;
        //部门信息
        private Dept dept;
    
        public void setEmpNo(String empNo) {
            this.empNo = empNo;
        }
    
        public void setEmpName(String empName) {
            this.empName = empName;
        }
    
        public void setDept(Dept dept) {
            this.dept = dept;
        }
    
        @Override
        public String toString() {
            return "Employee{" +
                    "empNo='" + empNo + '\'' +
                    ", empName='" + empName + '\'' +
                    ", dept=" + dept +
                    '}';
        }
    }

![135876b39f5388c957d95884fd99722d.png][]

bean.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
           https://www.springframework.org/schema/beans/spring-beans.xsd">
    
    
        <bean id="employee" class="org.example.Employee">
            <property  name="empNo" value="001"></property >
            <property  name="empName" value="小王"></property >
            <property  name="dept">
                
                <bean class="org.example.Dept">
                    <property name="deptNo" value="004"></property >
                    <property  name="deptName" value="技术部"></property >
                </bean>
            </property >
        </bean>
    
    
    
    </beans>

![658939cdc3f87f4a4f5fc7ce9efd131c.png][]

执行：

package org.example;
    
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class Main
    {
        private static final Log LOGGER = LogFactory.getLog(Main.class);
    
        public static void main(String[] args)
        {
            //获取 ApplicationContext 容器
            ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
    
            //获取名为 employee 的 Bean
            Employee employee = context.getBean("employee", Employee.class);
    
            //通过日志打印信息
            LOGGER.info(employee.toString());
    
            System.out.println(employee.toString());
    
        }
    
    }

![57b38c5ea69d5c7cd24ae51c5915abda.png][]

执行结果：

![d227efca3cc77f9264e6beddbc125f45.png][]

=================================================================================

我们将定义在 <bean> 元素的 <property> 或 <constructor-arg> 元素内部的 Bean，称为“内部 Bean”。

###  ###

### setter 方式注入内部 Bean ###

我们可以通过 setter 方式注入内部 Bean。此时，我们只需要在 <bean> 标签下的 <property> 元素中，再次使用 <bean> 元素对内部 Bean 进行定义，格式如下。

![d3821171e17e83dae55ea50d07b6b819.png][]

注意： 内部 Bean 都是匿名的，不需要指定 id 和 name 的。即使制定了，IoC 容器也不会将它作为区分 Bean 的标识符，反而会无视 Bean 的 Scope 标签。

因此内部 Bean 几乎总是匿名的，且总会随着外部的 Bean 创建。内部 Bean 是无法被注入到它所在的 Bean 以外的任何其他 Bean 的。

##### 示例 #####

下面我们就通过一个实例，演示下如何使用 setter 方法注入内部 Bean。  
1. 参考《[第一个 Spring 程序][Spring]》，新建一个名为 my-spring-demo2 的 Java 项目。  
2. 在 net.biancheng.c 包中，创建一个名为 Dept 的类，代码如下。

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   <td> 
    <div> 
     <div> 
      <code>package</code>&nbsp; 
      <code>net.biancheng.c;</code> 
     </div> 
     <div> 
      <code>public</code>&nbsp; 
      <code>class</code>&nbsp; 
      <code>Dept { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>//部门编号</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>private</code>&nbsp; 
      <code>String deptNo;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>//部门名称</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>private</code>&nbsp; 
      <code>String deptName;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>void</code>&nbsp; 
      <code>setDeptNo(String deptNo) { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.deptNo = deptNo;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>void</code>&nbsp; 
      <code>setDeptName(String deptName) { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.deptName = deptName;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>@Override</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>String toString() { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>return</code>&nbsp; 
      <code>"Dept{"</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>"deptNo='"</code>&nbsp; 
      <code>+ deptNo + '\</code> 
      <code>''</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>", deptName='"</code>&nbsp; 
      <code>+ deptName + '\</code> 
      <code>''</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>'}'</code> 
      <code>;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

3. 在 net.biancheng.c 包下，创建一个名为 Employee 的类，代码如下。

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 <tbody> 
  <tr> 
   <td> 
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    </div> 
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   <td> 
    <div> 
     <div> 
      <code>package</code>&nbsp; 
      <code>net.biancheng.c;</code> 
     </div> 
     <div> 
      <code>public</code>&nbsp; 
      <code>class</code>&nbsp; 
      <code>Employee { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>//员工编号</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>private</code>&nbsp; 
      <code>String empNo;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>//员工姓名</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>private</code>&nbsp; 
      <code>String empName;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>//部门信息</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>private</code>&nbsp; 
      <code>Dept dept;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>void</code>&nbsp; 
      <code>setEmpNo(String empNo) { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.empNo = empNo;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>void</code>&nbsp; 
      <code>setEmpName(String empName) { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.empName = empName;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>void</code>&nbsp; 
      <code>setDept(Dept dept) { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.dept = dept;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>@Override</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>public</code>&nbsp; 
      <code>String toString() { </code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>return</code>&nbsp; 
      <code>"Employee{"</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>"empNo='"</code>&nbsp; 
      <code>+ empNo + '\</code> 
      <code>''</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>", empName='"</code>&nbsp; 
      <code>+ empName + '\</code> 
      <code>''</code>&nbsp; 
      <code>+</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>", dept="</code>&nbsp; 
      <code>+ dept +</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>'}'</code> 
      <code>;</code> 
     </div> 
     <div> 
      <code>&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>}</code> 
     </div> 
     <div> 
      <code>}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

4. 在 src 目录下创建 Spring 配置文件 Beans.xml，配置如下。

![06fac1aaf28fe73136df62a2827b12cc.png][]

5. 在 net.biancheng.c 包下，创建一个名为 MainApp 的类，代码如下。

![fbe47f9f9a6c43f08dc7ee350f8e98b6.png][]

6. 执行 MainApp 中的 main() 方法，控制台输出如下。

![4bf03af44cfcc2d197398a63d5ac478b.png][]

[fb5a3d6bde1db13313284ced04f340dd.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/917adf109a1d4d28bd1bd1a8e6c11e8b.png
[f4da531471a28a6a51346e53cca0c643.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/b189d726727f4f1fb5886f4c5198b16f.png
[135876b39f5388c957d95884fd99722d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/f541f299dc444d6e8affbd6d11b24a06.png
[658939cdc3f87f4a4f5fc7ce9efd131c.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/de31d641a80749b9aac4c6a0215fc0ea.png
[57b38c5ea69d5c7cd24ae51c5915abda.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/2f111ce3dd75444284d2cbe68410e4e8.png
[d227efca3cc77f9264e6beddbc125f45.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/2cc86e056b804a79a2d6be30fb9581dc.png
[d3821171e17e83dae55ea50d07b6b819.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/d375a5fced27498fb76f9aa7ec93fe72.png
[Spring]: http://c.biancheng.net/spring/first-spring.html
[06fac1aaf28fe73136df62a2827b12cc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/34ceb654b2984490a3463b89d4782c22.png
[fbe47f9f9a6c43f08dc7ee350f8e98b6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/5bbc2c03a4ca4bf2883ba63a502739b0.png
[4bf03af44cfcc2d197398a63d5ac478b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/67de6c4d56124455943eae8edf99c835.png