spring的xml方式配置bean全過程

更新時間：2026年03月16日 10:05:26 作者：月731

文章介紹了Spring框架中配置bean的四種情況：無參構(gòu)造方法、有參構(gòu)造方法、Setter方法和實現(xiàn)InitializingBean接口,還提到了IOC控制反轉(zhuǎn)、DI依賴注入和AOP面向切面編程是Spring的三大特性

配置bean的4種情況

無參構(gòu)造

首先定義UserDao，UserDaoImpl，UserService，UserServiceImpl如下

public interface UserDao {
}

public class UserDaoImpl implements UserDao {
}

public interface UserService {
    void normalMethod();
}

public class UserServiceImpl implements UserService, InitializingBean, DisposableBean {

    private UserDao userDao;

    public UserServiceImpl() {
        System.out.println("執(zhí)行UserServiceImpl無參構(gòu)造方法");
    }

    public UserServiceImpl(String name) {
        System.out.println("執(zhí)行UserServiceImpl有參構(gòu)造方法, name = " + name);
    }

    public void setUserDao(UserDao userDao) {
        System.out.println("自動依賴注入，設(shè)置UserDao");
        this.userDao = userDao;
    }

    @Override
    public void afterPropertiesSet() {
        System.out.println("執(zhí)行InitializingBean的afterPropertiesSet");
    }

    public void init() {
        System.out.println("執(zhí)行bean標(biāo)簽定義的初始化方法");
    }

    @Override
    public void normalMethod() {
        System.out.println("執(zhí)行普通業(yè)務(wù)方法");
    }

    @Override
    public void destroy() {
        System.out.println("執(zhí)行DisposableBean的destroy");
    }

    public void myDestroy() {
        System.out.println("執(zhí)行bean標(biāo)簽定義的銷毀方法");
    }
}

實例化UserDao的方式：

UserDao userDao = new UserDaoImpl();

以無參構(gòu)造方法配置bean的方式：

<bean id="userDao" class="com.yt.dao.impl.UserDaoImpl"/>

驗證

    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        UserDao userDao = (UserDao) context.getBean("userDao");
        System.out.println(userDao);
        // 輸出 com.yt.dao.impl.UserDaoImpl@103f852
    }

有參構(gòu)造

實例化UserService的方式：

UserService userService = new UserServiceImpl("yt");

以有參構(gòu)造方法配置bean的方式：

<bean id="userService"  class="com.yt.service.impl.UserServiceImpl">
        <constructor-arg name="name" value="yt"/>
</bean>

驗證

    public static void main(String[] args) {
       ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        System.out.println(context.getBean("userService"));
        // 輸出
        // 執(zhí)行UserServiceImpl有參構(gòu)造方法, name = yt
        // com.yt.service.impl.UserServiceImpl@179bb86
    }

依賴注入

IOC控制反轉(zhuǎn)，DI依賴注入，AOP面向切面編程是spring的三大特性。

配置bean時想要自動注入bean的屬性需要提供：bean要注入的對象對應(yīng)的setter方法，被注入的bean，property標(biāo)簽。

    <bean id="userService" class="com.yt.service.impl.UserServiceImpl">
        <constructor-arg name="name" value="yt"/>
        <property name="userDao" ref="userDao"/>
    </bean>
    <bean id="userDao" class="com.yt.dao.impl.UserDaoImpl"/>

驗證

    public static void main(String[] args) {
       ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        System.out.println(context.getBean("userService"));
        // 輸出
        // 執(zhí)行UserServiceImpl有參構(gòu)造方法, name = yt
        // 自動依賴注入，設(shè)置UserDao
        // com.yt.service.impl.UserServiceImpl@179bb86
    }

bean標(biāo)簽的屬性

<bean id="userService"
          name="aaa,bbb,ccc" // 別名，可起多個，getBean時可使用別名獲取
          class="com.yt.service.impl.UserServiceImpl"
          scope="prototype" // 默認(rèn)單例singleton，非默認(rèn)原型prototype，即每次獲取bean都是不同的實例
          lazy-init="true" //懶加載，只在獲取bean時生成bean，默認(rèn)非懶加載，啟動容器就創(chuàng)建bean
          init-method="init" // 指定類里面的一個方法為初始化方法
          destroy-method="myDestroy"> // 指定類里面的一個方法為銷毀方法，需要手動關(guān)閉容器才可看到執(zhí)行
    </bean>

實現(xiàn)bean的初始化方法和銷毀方法還有一種方式，實現(xiàn)InitializingBean, DisposableBean接口。bean標(biāo)簽指定的方法和實現(xiàn)接口的方法的執(zhí)行順序見運(yùn)行結(jié)果

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        System.out.println(context.getBean("userService"));
        userService.normalMethod();
        //當(dāng)scope是prototype的時候，對象的生存周期spring就不管了。只有在tomcat或者容器關(guān)閉的時候，由tomcat調(diào)用
        context.close();
    }
// 輸出
// 執(zhí)行UserServiceImpl無參構(gòu)造方法
// 執(zhí)行InitializingBean的afterPropertiesSet
// 執(zhí)行bean標(biāo)簽定義的初始化方法
// com.yt.service.impl.UserServiceImpl@179bb86
// 執(zhí)行普通業(yè)務(wù)方法

靜態(tài)工廠方法（字太多了，懶得寫了）

    <bean id="userService1" class="com.yt.factory.MyBeanFactory1" factory-method="getUserService"/>

實例工廠方法

    <bean id="myBeanFactory2" class="com.yt.factory.MyBeanFactory2"/>
    <bean id="userService2" factory-bean="myBeanFactory2" factory-method="getUserService" lazy-init="true"/>

綜合使用

記得導(dǎo)入坐標(biāo)，再到mybaits官方文檔的入門里面下一個xml配置文件模板，改成自己的，記得刪掉mappe標(biāo)簽，因為沒寫

我還是貼出來

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/bai"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.3.23</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.23</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

當(dāng)前版本為jdk8

    <!--配置數(shù)據(jù)源-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/bai"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </bean>
    
    <!--配置Connection-->
    <bean id="clazz" class="java.lang.Class" factory-method="forName">
        <constructor-arg name="className" value="com.mysql.jdbc.Driver"/>
    </bean>
    <bean id="connection" class="java.sql.DriverManager" factory-method="getConnection" scope="prototype">
        <constructor-arg name="url" value="jdbc:mysql://localhost:3306/bai"/>
        <constructor-arg name="user" value="root"/>
        <constructor-arg name="password" value="123456"/>
    </bean>
    
    <!--配置一個當(dāng)前時間-->
    <bean id="now" class="java.time.LocalDateTime" factory-method="now"/>
    <bean id="dateTimeFormatter" class="java.time.format.DateTimeFormatter" factory-method="ofPattern">
        <constructor-arg name="pattern" value="yyyy-MM-dd HH:mm:ss"/>
    </bean>
    <bean id="nowString" factory-bean="now" factory-method="format">
        <constructor-arg name="formatter" ref="dateTimeFormatter"/>
    </bean>

    <!--配置一個SqlSessionFactory-->
    <bean id="mybatisConfigInputStream" class="org.apache.ibatis.io.Resources" factory-method="getResourceAsStream">
        <constructor-arg name="resource" value="mybatis-config.xml"/>
    </bean>
    <bean id="sqlSessionFactoryBuild" class="org.apache.ibatis.session.SqlSessionFactoryBuilder"/>
    <bean id="sqlSessionFactory" factory-bean="sqlSessionFactoryBuild" factory-method="build">
        <constructor-arg name="inputStream" ref="mybatisConfigInputStream"/>
    </bean>

驗證

public class ThirdPartyBeanTest {
    public static void main(String[] args) throws Exception {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        System.out.println(context.getBean("dataSource"));
        System.out.println(context.getBean("connection"));
        System.out.println(context.getBean("connection"));
        System.out.println(context.getBean("nowString"));
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sqlSessionFactory = builder.build(is);
        System.out.println(sqlSessionFactory);
        System.out.println(context.getBean("sqlSessionFactory"));
    }
}
// 輸出
{
	CreateTime:"2022-11-10 23:53:05",
	ActiveCount:0,
	PoolingCount:0,
	CreateCount:0,
	DestroyCount:0,
	CloseCount:0,
	ConnectCount:0,
	Connections:[
	]
}
Thu Nov 10 23:53:05 CST 2022 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
com.mysql.jdbc.JDBC4Connection@1af006c
Thu Nov 10 23:53:07 CST 2022 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
com.mysql.jdbc.JDBC4Connection@1d1433e
2022-11-10 23:53:05
org.apache.ibatis.session.defaults.DefaultSqlSessionFactory@46293d
org.apache.ibatis.session.defaults.DefaultSqlSessionFactory@1997e9d

Process finished with exit code 0