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2021
09-24

JAVA MyBatis入门学习过程记录

一、Mybatis

1、mybatis-config.xml

<?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>
<!--    外部引入db-->
    <properties resource="db.properties"/>
    <settings>
<!--        配置日志文件-->
<!--        <setting name="logImpl" value="STDOUT_LOGGING"/>-->
        <setting name="logImpl" value="log4j"/>
<!--        开启A_NAME==>aName-->        
        <setting name="mapUnderscoreToCamelCase" valie="true"
    </settings>
<!--   减少类型-->
    <typeAliases>        <typeAlias type="com.wang.pojo.User" alias="User"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/wang/dao/UserMapper.xml"/>
    </mappers>
</configuration>

2、Mapper.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="com.wang.dao.UserDao">
    <select id="getUserList" resultType="User">
        select * from mybatis.user
    </select>
</mapper>

3、db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis
username=root
password=123456

4、MybatisUtils工具类

package com.wang.utils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        InputStream inputStream = null;
        try {
            String resource = "mybatis-config.xml";
            inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getsqlsession() {
        return sqlSessionFactory.openSession();
    }
}

5、多对一AND多对一：

在Mapper.xml中配置

association 对象 多对一

collection 集合 一对多

从用参数解释：

  •  javaType java类型
  • ofType 泛型约束类型

6、使用注解开发

可在接口中使用注解进行开发，省去Mapper.xml

@Select("select * from mybatis.User")
List<User> getUserList();
在mybatis-config.xml中配置
<mappers>
        <mapper class="com.wang.Dao.UserMapper"
</mappers>

7、自定义缓存：ehcache

8、mybatis 其他工具

mybatis Hepler：https://pagehelper.github.io/

二、MAVEN资源导出错误解决

<build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

三、常用依赖导入

    <!--导入依赖-->
    <dependencies>
        <!--    mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <!--        mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--        junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
        </dependency>
<!--        lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>
<!--        servlet and jsp-->
        <dependency>
            <groupId>org.mortbay.jetty</groupId>
            <artifactId>servlet-api-2.5</artifactId>
            <version>6.1.7</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
        </dependency>
<!--        standard-->     
        <dependency>
            <groupId>org.apache.karaf.assemblies.features</groupId>
            <artifactId>standard</artifactId>
            <version>2.4.4</version>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
<!--        jstl-->       
        <dependency>
            <groupId>javax.servlet.jsp.jstl</groupId>
            <artifactId>jstl-api</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>jstl-impl</artifactId>
            <version>1.2</version>
        </dependency>
 <!--        fastjson-->    
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>
        <!--Log4j-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

四、LOG4J

1、log4j.properties 配置文件

    <!--导入依赖-->
    <dependencies>
        <!--    mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <!--        mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--        junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
        </dependency>
<!--        lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>
<!--        servlet and jsp-->
        <dependency>
            <groupId>org.mortbay.jetty</groupId>
            <artifactId>servlet-api-2.5</artifactId>
            <version>6.1.7</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
        </dependency>
<!--        standard-->     
        <dependency>
            <groupId>org.apache.karaf.assemblies.features</groupId>
            <artifactId>standard</artifactId>
            <version>2.4.4</version>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
<!--        jstl-->       
        <dependency>
            <groupId>javax.servlet.jsp.jstl</groupId>
            <artifactId>jstl-api</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>jstl-impl</artifactId>
            <version>1.2</version>
        </dependency>
 <!--        fastjson-->    
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>
        <!--Log4j-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

2、log4j 在mybatis-config.xml的配置

<settings>
        <setting name="logImpl" value="LOG4J"/>
</settings>

3、使用场景

在具体类中引入

Logger logger = Logger.getLogger(UserDaoTest.class);
logger.error();
logger.debug();

好用的插件：

1、lombok

常用注解：

  • @Data 自动生成geter seter
  • @AllArgsConstructor 生成有参构造函数
  • @NoArgsConstructor 生成无参构造函数

=“logImpl” value=“LOG4J”/>

## 3、使用场景

- 在具体类中引入

  ```java
  Logger logger = Logger.getLogger(UserDaoTest.class);
  logger.error();
  logger.debug();

常用注解：

  • @Data 自动生成geter seter
  • @AllArgsConstructor 生成有参构造函数
  • @NoArgsConstructor 生成无参构造函数

总结

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