Mybatis细节处理之mapper.xml的存放，properties配置文件，类型别名以及创建log4j配置文件

ゞ浴缸里的玫瑰 2023-01-20 10:56 14阅读 0赞

## 一.解决mapper.xml存放在resources以外路径中的读取问题 ##

在pom.xml文件最后追加< build >标签，以便可以将xml文件复制到classes中，并在程序运行时正确读取。

<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>

## 二.properties配置文件 ##

### 1.对于mybatis-config.xml的核心配置中，如果存在需要频繁改动的数据内容，可以提取到properties中。 ###

#jdbc.properties
    driver=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost:3306/example?useUnicode=true&characterEncpding=utf8
    username=root
    password=123456

#jdbc.properties
    #有多个.properties文件时可以加上jdbc，则对应的mybatis-config.xml中${jdbc.driver}...
    jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/example?useUnicode=true&characterEncpding=utf8
    jdbc.username=root
    jdbc.password=123456

### 2.修改mybatis-config.xml。注意！[properties至于顶部][properties](点击) ###

<?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="jdbc.properties" />
    
        <environments default="MySqlDB">
            <environment id="MySqlDB">
                <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="UserDaoMapper.xml" />
        </mappers>
    </configuration>

## 三.类型别名 ##

为实体类定义别名，提高书写效率。

<?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 ... />
        
        
        <typeAliases>
            
            <typeAlias type="com.cos.entity.User" alias="user" />
            
            
            <package name="com.cos.entity" />
        </typeAliases>
      
      	...
    </configuration>

## 四.创建log4j配置文件 ##

1.pom.xml添加log4j依赖

<dependency>
    		<groupId>log4j</groupId>
    		<artifactId>log4j</artifactId>
    		<version>1.2.17</version>
    </dependency>

2.创建并配置log4j.properties

# Global logging configuration
    log4j.rootLogger=DEBUG, stdout
    # MyBatis logging configuration...
    log4j.logger.org.mybatis.example.BlogMapper=TRACE
    # Console output...
    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

[properties]: https://blog.csdn.net/qwq1518346864/article/details/116702608?spm=1001.2014.3001.5501