# java-mybatis-study

**Repository Path**: cqjtu_admin/java-mybatis-study

## Basic Information

- **Project Name**: java-mybatis-study
- **Description**: myibatis 学习记录案例 希望能够坚持下去
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-04-13
- **Last Updated**: 2022-10-07

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# java-mybatis-study

#### 介绍
mybatis 学习记录案例 希望能够坚持下去

#### maven配置
```xml
<dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.6</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.15</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
```


#### 创建mybatis配置文件
```xml
<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/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=GMT%2B8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
```

#### 创建SqlSessionFactory
```java
String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
```

#### 创建mapper.xml
```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.xukai.dao.UserDao">
   <select id="getUserList" resultType="com.xukai.pojo.User">
       select * from mybatis.user
   </select>
</mapper>
```
#### 使用
```java
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
List<User> userList = mapper.getUserList();
```
#### 注意（可能出现的问题）
1. 当报一下错误时 mapper.xml 文件打包错误 
```
### Error building SqlSession.
### The error may exist in UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource UserMapper.xml
```
解决办法：
  *** 1. 将mapper.xml 放在resoureces文件夹下
  *** 2. 在pom.xml 文件中增加如下配置
```xml
 <!--在build中配置resources 来防止将来资源导出失败 -->
  <build>
      <resources>
          <resource>
              <directory>src/main/resources</directory>
              <includes>
                  <include>**/*.properties</include>
                  <include>**/*.xml</include>
              </includes>
              <filtering>true</filtering>
          </resource>
          <resource>
              <directory>com/xukai/dao</directory>
              <includes>
                  <include>**/*.properties</include>
                  <include>**/*.xml</include>
              </includes>
              <filtering>true</filtering>
          </resource>
      </resources>
  </build>
```

#### crud
   1. 查询

```xml
      <select id="getUserList" resultType="com.xukai.pojo.User">
      select * from mybatis.user
      </select>
   ```
  2. update
  ```xml
 <update id="update" parameterType="com.xukai.pojo.User">
        update  user  set username = #{username},pwd=#{pwd} where id = #{id}
    </update>
```
  3. insert
```xml
 <insert id="insert" parameterType="com.xukai.pojo.User">
        insert user(id,username,pwd) values (#{id},#{username},#{pwd})
    </insert>
```
 4. delete
```xml
<delete id="delete">
        delete from user where id = #{id}
    </delete>
```
 5. 注意
    update delete insert  执行后记得提交事务
    
    ```javasqlSession.commit();```
### mybaties配置
#### properties
这些属性可以在外部进行配置，并可以进行动态替换。你既可以在典型的 Java 属性文件中配置这些属性，也可以在 properties 元素的子元素中设置
例如
```xml
 <properties resource="db.properties">
    </properties>
```
db.properties文件如下
```properties
    driver=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8
    username=root
    password=123456
```
mybatis-config.xml配置如下：
```xml
 <dataSource type="POOLED">
    <property name="driver" value="${driver}"/>
    <property name="url" value="${url}"/>
    <property name="username" value="${username}"/>
    <property name="password" value="${password}"/>
</dataSource>
```
#### setting设置 
##### 日志设置
1. 默认使用mybatis自带的STDOUT_LOGGING
```xml
<settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
```
2. 使用log4j日志
###### log4j包
```xml
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
```
###### log4.properties
```properties
#############
# 输出到控制台
#############

# log4j.rootLogger日志输出类别和级别：只输出不低于该级别的日志信息DEBUG < INFO < WARN < ERROR < FATAL
# WARN：日志级别     CONSOLE：输出位置自己定义的一个名字       logfile：输出位置自己定义的一个名字
log4j.rootLogger=DEBUG,CONSOLE,logfile
# 配置CONSOLE输出到控制台
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender 
# 配置CONSOLE设置为自定义布局模式
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout 
# 配置CONSOLE日志的输出格式  [frame] 2019-08-22 22:52:12,000  %r耗费毫秒数 %p日志的优先级 %t线程名 %C所属类名通常为全类名 %L代码中的行号 %x线程相关联的NDC %m日志 %n换行
log4j.appender.CONSOLE.layout.ConversionPattern=[frame] %d{yyyy-MM-dd HH:mm:ss,SSS} - %-4r %-5p [%t] %C:%L %x - %m%n

################
# 输出到日志文件中
################

# 配置logfile输出到文件中 文件大小到达指定尺寸的时候产生新的日志文件
log4j.appender.logfile=org.apache.log4j.RollingFileAppender
# 保存编码格式
log4j.appender.logfile.Encoding=UTF-8
# 输出文件位置此为项目根目录下的logs文件夹中
log4j.appender.logfile.File=logs/root.log
# 后缀可以是KB,MB,GB达到该大小后创建新的日志文件
log4j.appender.logfile.MaxFileSize=10MB
# 设置滚定文件的最大值3 指可以产生root.log.1、root.log.2、root.log.3和root.log四个日志文件
log4j.appender.logfile.MaxBackupIndex=3  
# 配置logfile为自定义布局模式
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %F %p %m%n

##########################
# 对不同的类输出不同的日志文件
##########################

## club.bagedate包下的日志单独输出
#log4j.logger.club.bagedate=DEBUG,bagedate
## 设置为false该日志信息就不会加入到rootLogger中了
#log4j.additivity.club.bagedate=false
## 下面就和上面配置一样了
#log4j.appender.bagedate=org.apache.log4j.RollingFileAppender
#log4j.appender.bagedate.Encoding=UTF-8
#log4j.appender.bagedate.File=logs/bagedate.log
#log4j.appender.bagedate.MaxFileSize=10MB
#log4j.appender.bagedate.MaxBackupIndex=3
#log4j.appender.bagedate.layout=org.apache.log4j.PatternLayout
#log4j.appender.bagedate.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %F %p %m%n


#4 mybatis 显示SQL语句部分
log4j.logger.org.mybatis=DEBUG
#log4j.logger.cn.tibet.cas.dao=DEBUG
#log4j.logger.org.mybatis.common.jdbc.SimpleDataSource=DEBUG
#log4j.logger.org.mybatis.common.jdbc.ScriptRunner=DEBUG
#log4j.logger.org.mybatis.sqlmap.engine.impl.SqlMapClientDelegate=DEBUG
#log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

```
##### mybaties-config.xml
```xml
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
```

#### 注意在mybatis-config.xml中各属性配置具有严格的先后顺序

### 结果集映射 当从数据库中查询到的数据项字段名与pojo（普通的老的java对象） 不一致时 需要使用结果集映射
```xml
<resultMap id="userResultMap" type="com.xukai.pojo.User">
        <result property="username" column="name"/>
    </resultMap>
    <select id="getUser" resultMap="userResultMap">
        select * from user where id = #{id}
    </select>
```