spring——Spring 注入内部Bean——构造函数方式注入内部 Bean

缺乏、安全感 2024-03-31 17:23 82阅读 0赞

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>

![63a0646dd2e2220b1c9fc26d676849b7.png][]

dept类：

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

![077256c8dc7f3afbabd55de549b744a9.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 Employee(String empNo, String empName, Dept dept) {
            this.empNo = empNo;
            this.empName = empName;
            this.dept = dept;
        }
    
    
        @Override
        public String toString() {
            return "Employee{" +
                    "empNo='" + empNo + '\'' +
                    ", empName='" + empName + '\'' +
                    ", dept=" + dept +
                    '}';
        }
    }

![4af3fc106c56718c9e042735a546c8a4.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">
            <constructor-arg name="empNo" value="002"></constructor-arg>
            <constructor-arg name="empName" value="小李"></constructor-arg>
            <constructor-arg name="dept">
                
                <bean class="org.example.Dept">
                    <constructor-arg name="deptNo" value="005"></constructor-arg>
                    <constructor-arg name="deptName" value="运维部"></constructor-arg>
                </bean>
            </constructor-arg>
        </bean>
    
    
    
    </beans>

![9d2f49956968a41cc9ba122683fb9cd0.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());
    
        }
    
    }

![ae873d25fabb92bdd732e327320eac14.png][]

执行结果：

![393d819c0d30b3cf6094609cb18ce479.png][]

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

### 构造函数方式注入内部 Bean ###

我们可以通过构造方法注入内部 Bean。此时，我们只需要在 <bean> 标签下的 <constructor-arg> 元素中，再次使用 <bean> 元素对内部 Bean 进行定义，格式如下。

![41a7bb29adbe59e1a22d902f201167bf.png][]

##### 示例 #####

下面我们就通过一个实例，演示下如何在通过构造方法的方式注入内部 Bean。  
1. 参考《[第一个 Spring 程序][Spring]》，新建一个名为 my-spring-demo3 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>Dept(String deptNo, String deptName) { </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;&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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    </div> </td> 
   <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>Employee(String empNo, String empName, Dept dept) { </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;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code>this</code> 
      <code>.empName = empName;</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。

![6de50bcdd230eabc1c5b9be844d31b76.png][]

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

![38e66694972569019eec021c631aef78.png][]

[63a0646dd2e2220b1c9fc26d676849b7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/767e6ade923746418b88d6e4dddb4c3e.png
[077256c8dc7f3afbabd55de549b744a9.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/71769af8f1764b1085d4a04c39df3dc9.png
[4af3fc106c56718c9e042735a546c8a4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/8932a4d425174176a81cbd2ef230a60d.png
[9d2f49956968a41cc9ba122683fb9cd0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/e6e7a9b494d846a1930c8297671f51fc.png
[ae873d25fabb92bdd732e327320eac14.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/bd7eba962e4348d0bdae647680c9044f.png
[393d819c0d30b3cf6094609cb18ce479.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/bed378f0f550439699a7e91dd375139c.png
[41a7bb29adbe59e1a22d902f201167bf.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/8cd059885aa54a1694a1903f6c8202a7.png
[Spring]: http://c.biancheng.net/spring/first-spring.html
[6de50bcdd230eabc1c5b9be844d31b76.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/6e1d8269adf440819ece553433d4e635.png
[38e66694972569019eec021c631aef78.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/b780ec1f2a894bdd990eb9e6cc875d4e.png