Maven资源导出的配置

!--   build中配置resources,防止资源导出失败-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
    
<!--   设置 property 变量 的编码为UTF-8 -->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

Mybatis-config.xml的配置

<?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>
    <!--引入配置文件  可以在其中添加一些配置 如果添加的属性配置与配置文件中属性配置同名 优先使用配置文件中的配置-->
    <properties resource="db.properties"></properties>
<!--    类型别名的配置-->
    <typeAliases>
<!--        给具体的类起一个别名-->
<!--        <typeAlias type="com.demo4.pojo.User" alias="User"></typeAlias>-->
<!--        也可以指定一个包名 MyBatis会在包中搜索需要的javaBan  包中所有的类的别名为类的首字母小写
            若有注解 则别名为其注解的值  
            @Alias("Hello")
            public class User {
            }  -->
        <package name="com.demo4.pojo"></package>
    </typeAliases>
   
<!--环境的配置-->
    <environments default="test">
        <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>

        <environment id="test">
            <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>

<!--  映射器的配置-->
    <mappers>
<!--        资源绑定 （推荐使用）-->
        <mapper resource="com/demo4/dao/UserMapper.xml"></mapper>
<!--        类绑定  接口和她的mapper配置文件必须同名 接口和她的mapper配置文件必须在同一个包下-->
<!--        <mapper class="com.demo4.dao.UserMapper"></mapper>-->
<!--      扫描包绑定  接口和她的mapper配置文件必须同名 接口和她的mapper配置文件必须在同一个包下   -->
<!--        <package name="com.demo4.dao"></package>-->
    </mappers>

</configuration>

MybatisUtils工具类

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static  {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

映射的配置

<?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.mybatis.dao.UserMapper">
    <select id="getUserList" resultType="com.mybatis.pojo.User">
        select * from user
      </select>

    <select id="getUser" parameterType="int" resultType="com.mybatis.pojo.User">
    select * from user where id = #{id}
  </select>
<!--    添加-->
    <insert id="insertUser" parameterType="com.mybatis.pojo.User">
        insert into user(id,name,pwd) values(#{id},#{name},#{pwd})
    </insert>
<!--修改-->
    <update id="updateUser" parameterType="com.mybatis.pojo.User">
        update user set name=#{name},pwd=#{pwd} where id = #{id}
    </update>
<!--    删除-->
    <delete id="deleteUserById" parameterType="int">
        delete from user where id = #{id}
    </delete>
</mapper>


//注意点 增删改需要提交事务

数据库中的字段与实体类属性不一致的解决办法

1、在sql语句中对字段与属性不一样的字段起别名
//实体类
public class User {
   private int id;
   private String name;
   private String password;
}
//数据库中的字段 id name pwd
//配置的sql语句
 <select id="getUser" resultType="user" parameterType="_int">
        select id,name,pwd as password from user where id = #{id}
    </select>
2、resultMap
   <resultMap id="userMap" type="user">
<!-- column代表数据库中的字段 property代表实体类中的属性-->
      <result column="id" property="id"></result>
        <result column="name" property="name"></result>
        <result column="pwd" property="password"></result>
    </resultMap>
    <select id="getUser" parameterType="_int"  resultMap="userMap">
        select * from user where id = #{id}
    </select>

Log4j的使用

1、引入依赖
<dependency>
      <groupId>log4j</groupId>
     <artifactId>log4j</artifactId>
     <version>1.2.17</version>
</dependency>
2、创建配置文件log4j.properties 进行配置
log4j.rootLogger=DEBUG,console,file

#控制台输出的配置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold = DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern = [%c]-%m%n

#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File = ./log/zhang.log
log4j.appender.file.MaxFileSize = 10mb
log4j.appender.file.Threshold = DEBUG
log4j.appender.file.layout = org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern = [%p][%d{yy-MM-dd}]{%c}%m%n

#日志输出级别
log4j.logger.org.mybatis = DEBUG
log4j.logger.java.sql = DEBUG
log4j.logger.java.sql.Statement = DEBUG
log4j.logger.java.sql.ResultSet = DEBUG
log4j.logger.java.sql.PreparedStatement = DEBUG
3、在mybatis-config.xml文件中进行设置
<!--    设置-->
    <settings>
<!--        配置标准的日志工厂-->
<!--        <setting name="logImpl" value="STDOUT_LOGGING"></setting>-->
<!--        配置log4j日志工厂-->
        <setting name="logImpl" value="LOG4J"></setting>
    </settings>

4、在需要使用log4j的类中到包  import org.apache.log4j.Logger;
  参数为  当前类.class
 private static Logger logger = Logger.getLogger(参数);

5、日志级别
logger.info("info: Log4jTest");
logger.debug("info: Log4jTest");
logger.error("info: Log4jTest");

使用注解（适合简单的sql语句）

1、
public interface UserMapper {
    @Select("select * from user")
    List<User> getUserList();
    
   //方法存在多个参数时 要加@Param("id")的注解
   //关于@Param()注解 
   //基本类型和String类型的参数要加
   //引用类型不需添加
   //如果只有一个基本类型的可以忽略 但建议加上

    @Select("select * from user where id = #{id}")
    User getUser(@Param("id") int id);

    @Insert("insert into user(id,name,pwd) values(#{id},#{name},#{password})")
    int insertUser(User user);

    @Update("update user set name=#{name},pwd=#{password} where id = #{id}")
    int updateUser(User user);

    @Delete("delete from user where id = #{id}")
    int deleteUser(int id);
}
2、在mybatis-config.xml中绑定接口

  <mappers>
      <mapper class="com.demo5.dao.UserMapper"></mapper>
  </mappers>

mybatis的执行流程

设置自动提交事务

    // sqlSessionFactory.openSession(true); 参数设置为true会自动提交事务
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession(true);
    }

多表查询（多对一）

例如
多个学生对应一个老师
public class Student {
    private int id;
    private String name;
    private int tid;
    private Teacher teacher;
}
public class Teacher {
    private int id;
    private Striing name
}

sql语句
  <select id="getStudentList2" resultMap="StudentTeacher2">
        select s.id sid,s.name sname,t.name tname
        from Student s,teacher t
        where s.tid = t.id
    </select>
    <resultMap id="StudentTeacher2" type="Student">
        <result property="id" column="sid"></result>
        <result property="name" column="sname"></result>
        //javaType 是属性的类型 oftype为属性的泛型的类型
        <association property="teacher" javaType="Teacher">
            <result property="name" column="tname"></result>
        </association>
    </resultMap>
  
或

    <select id="getStudentList" resultMap="StudentTeacher">
      select * from student
    </select>
    <resultMap id="StudentTeacher" type="Student">
        <result property="id" column="id"></result>
        <result property="name" column="name"></result>
        <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"></association>
    </resultMap>

    <select id="getTeacher" resultType="Teacher">
        select * from teacher where id = #{id}
    </select>

多表查询（一对多）

public class Student {
    private int id;
    private String name;
    private int tid;
}

public class Teacher {
   private int id;
   private String name;
   private List<Student> students;
}

sql查询

 <select id="getTeacher" resultMap="TeacherStudent">
        select s.id sid,s.name sname,t.id tid,t.name tname
        from student s,teacher t
        where s.tid = t.id and t.id = #{id}
     </select>

    <resultMap id="TeacherStudent" type="Teacher">
        <result property="id" column="tid"></result>
        <result property="name" column="tname"></result>
        <collection property="list" ofType="Student">
            <result property="id" column="sid"></result>
            <result property="name" column="sname"></result>
            <result property="tid" column="tid"></result>
        </collection>
    </resultMap>

或

   <select id="getTeacher" resultMap="TeacherStudent2">
        select * from teacher where id = #{id}
    </select>

    <resultMap id="TeacherStudent2" type="Teacher">
        <collection property="list" javaType="ArrayList" ofType="Student"  select="getStudent" column="id"></collection>
    </resultMap>

    <select id="getStudent" resultType="Student">
        select * from student where tid = #{tid}
    </select>

动态Sql(利用相应的标签来拼接不同条件下的sql语句)

public interface BlogMapper {

    int insertBlog(Blog blog);

    List<Blog> getBlogList(Map<String,Object> map);

    int updateBlog(Map<String,Object> map);

    List<Blog> getBlogForEach(Map<String,Object> map);
}

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.demo8.dao.BlogMapper">
    <insert id="insertBlog" parameterType="Blog">
        insert into blog(id,title,author,create_time,views) values(#{id},#{title},#{author},#{createTime},#{views})
    </insert>

    <select id="getBlogList" parameterType="map" resultType="Blog">
        select * from blog
        <where>
<!--            <if test="title != null" >-->
<!--                title = #{title}-->
<!--            </if>-->
<!--            <if test="author != null">-->
<!--                and author = #{author}-->
<!--            </if>-->
            <choose>
                <when test="title != null">
                    title = #{title}
                </when>
                <when test="author != null">
                    and author = #{author}
                </when>
                <otherwise>
                    and views = #{views}
                </otherwise>
            </choose>
        </where>
    </select>

<!--     sql标签抽取公共的sql语句 提高复用性-->
    <sql id="if-title-author">
        <if test="title != null">
            title = #{title},
        </if>
        <if test="author != null">
            author = #{author}
        </if>
    </sql>

    <update id="updateBlog" parameterType="map">
        update blog
        <set>
            <!-- 引用抽取的公共sql语句-->
            <include refid="if-title-author"></include>
        </set>
        where id = #{id}
    </update>


    <select id="getBlogForEach" parameterType="map" resultType="Blog">
        select * from blog
        where id in
        <foreach collection="ids" item="id" open=" (" close=")" separator=",">
            #{id}
        </foreach>

    </select>
</mapper>

测试foreach的的代码
 @Test
    public void test3() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        Map<String,Object> map = new HashMap<String, Object>();
        List<Integer> ids = new ArrayList<Integer>();
        ids.add(1);
        ids.add(2);
        ids.add(3);
        ids.add(4);
        map.put("ids",ids);
        List<Blog> blogForEach = mapper.getBlogForEach(map);
        for (Blog blog : blogForEach) {
            System.out.println(blog);
        }
        sqlSession.close();
    }

开启全局缓存

 1、在mybatis-config.xml配置文件中设置开启全局缓存
 <settings>
        <setting name="logImpl" value="LOG4j"></setting>
        <!--开启驼峰命名自动转换-->
        <setting name="mapUnderscoreToCamelCase" value="true"></setting>
<!--        开启全局缓存-->
        <setting name="cacheEnabled" value="true"></setting>
    </settings>
2、//默认情况下，只启用了本地的会话缓存（一级），它仅仅对一个会话中的数据进行缓存。 要启用全局的二级缓存，只需要在你的 SQL 映射文件中添加一行
  <cache eviction="FIFO"
            flushInterval="60000"
            size="512"
            readOnly="true"/>
3、<select useCache="true"></seclect>
注意:
>只要开启二级缓存，在用一个映射文件下有效
>所有的数据会先放在一级缓存中
>只有当会话提交，或关闭时才会提交到耳机缓存中