FactoryBean的两种实现方法（以Mybatis中的SqlSessionFactory为例)

缺乏、安全感 2023-07-03 12:05 10阅读 0赞

在spring中，FactoryBean用于构造复杂的对象，如Connection,SqlSession等，本文以构建SqlSession为例

首先准备如下代码：

数据库配置文件：databases.properties

#连接设置
    driverClassName=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost:3306/test?useSSL=true
    username=root
    password=xxxxxxxx
    #
    initialSize=10
    #最大连接数量
    maxActive=50
    #
    minIdle=5
    #
    maxWait=5000

一个Entity:StudentInfo.java

public class StudentInfo {
    
        private String student_id;
        private String student_name;
        private String student_major;
        private String student_gender;
        private java.sql.Date student_birthday;
    
    }

StduentInfo对应的dao层接口：StudentDao.java

public interface StudentDao {
        /**
         * 根据id查询用户信息
         *
         * @param id
         * @return
         */
        public StudentInfo queryStudentById(String id);
    }

StudentDao.java的mybatis的映射：StudentDaoMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="org.example.dao.StudentDao">
    
        <select id="queryStudentById" resultType="org.example.entity.StudentInfo">
            SELECT *
            FROM test.student_info
            WHERE student_id = #{student_id};
        </select>
    
    </mapper>

最后就是MyBatis的配置文件:mybatis-config.xml(将mapper添加其中)

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    
    <configuration>
        <properties resource="mybatis/database.properties"/>
    
        
        <environments default="test">
            
            <environment id="test">
                
                <transactionManager type="JDBC"/>
                
                <dataSource type="POOLED">
                    <property name="driver" value="${driverClassName}"/>
                    <property name="url" value="${url}"/>
                    <property name="username" value="${username}"/>
                    <property name="password" value="${password}"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper resource="mybatis/mapper/StudentDaoMapper.xml"/>
        </mappers>
    </configuration>

**经过以上准备，我们现在就可以通过mybatis-config.xml来获取SqlSessionFactory对象了**

# 方法一：实现FactoryBean接口 #

新建SqlSessionFactoryBean.java ,使其实现FactoryBean接口

package org.example.factoryBean;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.springframework.beans.factory.FactoryBean;
    
    import java.io.InputStream;
    
    /**
     * 生产SqlSessionFactory对象
     */
    public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory> {
        //完成复杂对象的生产，并返回该对象
        @Override
        public SqlSessionFactory getObject() throws Exception {
            InputStream inputStream= Resources.getResourceAsStream("mybatis/mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
            return sqlSessionFactory;
        }
    
        //返回复杂对象的类对象
        @Override
        public Class<?> getObjectType() {
            return SqlSessionFactory.class;
        }
    
        //控制复杂对象的创建模式,（返回true为单例模式，返回false为多例（原型）模式）
        @Override
        public boolean isSingleton() {
            return true;
        }
    }

在applicationContext.xml中配置如下<bean>

![20200206121949207.png][]

即可在工厂中获取该对象

# 方法二：静态工厂方法 #

修改对象SqlSessionFactoryBean.java

package org.example.factoryBean;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.InputStream;
    
    /**
     * 生产SqlSessionFactory对象
     */
    public class SqlSessionFactoryBean {
        //完成复杂对象的生产，并返回该对象
        public static SqlSessionFactory getObject() throws Exception {
            InputStream inputStream = Resources.getResourceAsStream("mybatis/mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            return sqlSessionFactory;
        }
    }

在applicationContext.xml中配置如下<bean>

![20200206122418149.png][]

**谢谢观看！**

[20200206121949207.png]: https://img-blog.csdnimg.cn/20200206121949207.png
[20200206122418149.png]: https://img-blog.csdnimg.cn/20200206122418149.png