這次我們一起來做一個入門級別的持久層框架Mybatis的配置，正所謂完事開頭難。

1 引入依賴

     <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.6</version>
        </dependency>

        <dependency>
            <groupId
 
>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
        </dependency>

       //列印日誌用
       <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId
 
>
            <version>1.2.17</version>
        </dependency>


        //測試用
       <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope
 
>
        </dependency>

 <!-- 配置很多外掛 -->
        <plugins>
            <plugin>
                <!-- maven外掛 -->
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <!-- 配置jdk版本 -->
                    <source>1.8</source>
                    <target>1.8</target>
                    <!-- 配置編碼 -->
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>

         <resources>
             <resource>
                 <!-- 配置打war時候的要打的檔案路徑 -->
                 <directory>src/main/java</directory>
                 <includes>
                     <!-- 打入所有.class .xml結尾的檔案，maven預設是將resources目錄下的檔案在構建的時候一起打包，例如，*.xml之類的檔案，如果要放在java目錄下面的話，就要在這裡告訴maven了 -->
                     <include>**/*.class</include>
                     <include>**/*.xml</include>
                 </includes>

             </resource>

         </resources>

2 配置mybatis的配置檔案

<configuration>
//這些標籤都是有固定順序的，這個阿帕奇要求的，用別人的東西，當然要遵守別人的遊戲規則。

//引入外部配置檔案，下面的${jdbc.dataSource}這些就是獲取外部配置檔案的值，這樣做的好處就是不用每次來修改mybatis的配置檔案，只要在外部得properties檔案中配置即可；
    <properties resource="settings.properties"/>

    <!-- 和spring整合後 environments配置將廢除 -->
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事務管理 -->
            <transactionManager type="${jdbc.transactionManager}"/>
            <!-- 資料庫連線池 -->
            <dataSource type="${jdbc.dataSource}">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url"
                          value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 載入sqlmap檔案 -->
    <mappers>
        <mapper resource="com/quyang/my/sqlmap/BaseUserMap.xml"/>
    </mappers>
</configuration>

3 編寫sql檔案

<?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">
        //這裡的namespace最好用介面的全路徑，實際開發中大多都是面向介面的方式。這裡寫介面的全路徑就是指介面和這個sql檔案進行了繫結。
<mapper namespace="com.quyang.my.map.BaseUserMapa">

//查詢語句，這個檔案怎麼來寫，這裡就不多說了，很簡單的，不懂百度
    <select id="selectBaseUserById" parameterType = "Integer" resultType="com.quyang.my.BaseUser">
        select * from base_user where user_id = #{iddd}
    </select>
</mapper>

4 外部配置檔案

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/user?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456
jdbc.transactionManager=JDBC
jdbc.dataSource=POOLED

可以和上面的mybatis的配置檔案對照來看。

5 日誌檔案配置

# Global logging configuration 輸出debug級別以上
log4j.rootLogger=DEBUG, stdout
# Console output... log輸出到控制檯，ConsoleAppender表示log輸出到控制檯
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
# log佈局
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
# 輸入格式
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

6 測試

  public void testApp() {
        try {
        //首先就是要建在mybatis的配置檔案
            InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
            SqlSession sqlSession = sessionFactory.openSession();
            //獲取介面的例項，實質是一個代理物件；
            BaseUserMapa selectOne = sqlSession.getMapper(BaseUserMapa.class);
            //呼叫介面的方法查表
            BaseUser baseUser = selectOne.selectBaseUserById(10000);
            System.out.println("AppTest.testApp=" + baseUser.getName());

        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("AppTest.error");
        }
    }

7 結果

E:\jdk\set\bin\java -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:D:\ideaUI\lib\idea_rt.jar=49322:D:\ideaUI\bin -Dfile.encoding=UTF-8 -classpath D:\ideaUI\lib\idea_rt.jar;D:\ideaUI\plugins\junit\lib\junit-rt.jar;D:\ideaUI\plugins\junit\lib\junit5-rt.jar;E:\jdk\set\jre\lib\charsets.jar;E:\jdk\set\jre\lib\deploy.jar;E:\jdk\set\jre\lib\ext\access-bridge-64.jar;E:\jdk\set\jre\lib\ext\cldrdata.jar;E:\jdk\set\jre\lib\ext\dnsns.jar;E:\jdk\set\jre\lib\ext\jaccess.jar;E:\jdk\set\jre\lib\ext\jfxrt.jar;E:\jdk\set\jre\lib\ext\localedata.jar;E:\jdk\set\jre\lib\ext\nashorn.jar;E:\jdk\set\jre\lib\ext\sunec.jar;E:\jdk\set\jre\lib\ext\sunjce_provider.jar;E:\jdk\set\jre\lib\ext\sunmscapi.jar;E:\jdk\set\jre\lib\ext\sunpkcs11.jar;E:\jdk\set\jre\lib\ext\zipfs.jar;E:\jdk\set\jre\lib\javaws.jar;E:\jdk\set\jre\lib\jce.jar;E:\jdk\set\jre\lib\jfr.jar;E:\jdk\set\jre\lib\jfxswt.jar;E:\jdk\set\jre\lib\jsse.jar;E:\jdk\set\jre\lib\management-agent.jar;E:\jdk\set\jre\lib\plugin.jar;E:\jdk\set\jre\lib\resources.jar;E:\jdk\set\jre\lib\rt.jar;D:\eclipse\myweb\testmybatis\target\test-classes;D:\eclipse\myweb\testmybatis\target\classes;D:\repo\repository\junit\junit\3.8.1\junit-3.8.1.jar;D:\repo\repository\asm\asm\3.3.1\asm-3.3.1.jar;D:\repo\repository\cglib\cglib\2.2\cglib-2.2.jar;D:\repo\repository\commons-logging\commons-logging\1.2\commons-logging-1.2.jar;D:\repo\repository\javassist\javassist\3.11.0.GA\javassist-3.11.0.GA.jar;D:\repo\repository\log4j\log4j\1.2.17\log4j-1.2.17.jar;D:\repo\repository\org\apache\logging\log4j\log4j-api\2.5\log4j-api-2.5.jar;D:\repo\repository\org\apache\logging\log4j\log4j-core\2.5\log4j-core-2.5.jar;D:\repo\repository\org\mybatis\mybatis\3.2.6\mybatis-3.2.6.jar;D:\repo\repository\mysql\mysql-connector-java\5.1.38\mysql-connector-java-5.1.38.jar;D:\repo\repository\org\slf4j\slf4j-api\1.7.18\slf4j-api-1.7.18.jar;D:\repo\repository\org\slf4j\slf4j-log4j12\1.7.7\slf4j-log4j12-1.7.7.jar com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit3 com.quyang.my.AppTest,testApp
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
Sun Aug 20 19:29:46 GMT+08:00 2017 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.
DEBUG [main] - Created connection 1899073220.
DEBUG [main] - Setting autocommit to false on JDBC Connection [[email protected]]
DEBUG [main] - ==>  Preparing: select * from base_user where user_id = ? 
DEBUG [main] - ==> Parameters: 10000(Integer)
DEBUG [main] - <==      Total: 1
AppTest.testApp=13738860434

Process finished with exit code 0

可以看出，log4j將所有的資訊都打印出來了，包括查詢標的select語句和引數，結果，13738860434這個就是我查出來的本地mysql資料庫的資料；

8 要注意的問題

要搞清楚類路徑是什麼，一般我們寫一個類的話，檔案最上面會出現com.xxx.xxx,這就是檔案的路徑，而要寫一個類路徑下的檔案的話，寫出來的效果是，檔案做上面啥都沒有，也就是說沒有包名，就是在根目錄下。