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本文适合对mybatis有简单的入门了解的读者。转载请注明出处！
环境：
Mysql5.6、navicat for mysql 11、jdk8、maven3.3.9、mybatis3.2.8
MySQL表
CREATE TABLE `sale` ( `id` int(11) NOT NULL AUTO_INCREMENT, `sale_name` varchar(255) DEFAULT NULL, `sale_age` int(11) DEFAULT NULL, `user_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=gbk;
CREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `age` int(11) NOT NULL, `name` varchar(255) NOT NULL, `user_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=gbk;
maven依赖配置(pom.xml)
1 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 2 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> 3 <modelVersion>4.0.0</modelVersion> 4 <groupId>com</groupId> 5 <artifactId>batistest</artifactId> 6 <packaging>war</packaging> 7 <version>0.0.1-SNAPSHOT</version> 8 <name>batistest Maven Webapp</name> 9 <url>http://maven.apache.org</url> 10 <dependencies> 11 <dependency> 12 <groupId>junit</groupId> 13 <artifactId>junit</artifactId> 14 <version>3.8.1</version> 15 <scope>test</scope> 16 </dependency> 17 <dependency> 18 <groupId>org.mybatis</groupId> 19 <artifactId>mybatis</artifactId> 20 <version>3.2.8</version> 21 </dependency> 22 <dependency> 23 <groupId>mysql</groupId> 24 <artifactId>mysql-connector-java</artifactId> 25 <version>5.1.38</version> 26 </dependency> 27 <dependency> 28 <groupId>log4j</groupId> 29 <artifactId>log4j</artifactId> 30 <version>1.2.17</version> 31 </dependency> 32 </dependencies> 33 <build> 34 <finalName>batistest</finalName> 35 </build> 36 </project>
mybatis配置文件（conf.xml）
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> 3 <configuration> 4 <environments default="development"> 5 <environment id="development"> 6 <transactionManager type="JDBC" /> 7 <!-- 配置数据库连接信息 --> 8 <dataSource type="POOLED"> 9 <property name="driver" value="com.mysql.jdbc.Driver" /> 10 <property name="url" value="jdbc:mysql://localhost:3308/rfid" /> 11 <property name="username" value="admin" /> 12 <property name="password" value="dps2010_admin" /> 13 </dataSource> 14 </environment> 15 </environments> 16 17 <!-- 注册映射文件 --> 18 <mappers> 19 <mapper resource="demo/mybatis/base/mapper/User.xml" /> 20 <mapper resource="demo/mybatis/base/mapper/IUser.xml" /> 21 <mapper resource="demo/mybatis/base/mapper/IRelate.xml" /> 22 </mappers> 23 </configuration>
mybatis映射文件(demo/mybatis/base/mapper/User.xml)
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 3 <!-- 唯一命名空间，通常定义规则为：所在包名+文件名(映射文件) --> 4 <mapper namespace="demo.mybatis.base.mapper.User"> 5 6 <!-- 7 缓存启用 8 9 缓存更新算法 10 LRU － 最近最少使用的：移除最长时间不被使用的对象 11 FIFO － 先进先出：按对象进入缓存的时间顺序来移除 12 SOFT － 软引用：移除基于垃圾回收器状态和软引用规则的对象 13 WEAK － 弱引用：更积极地移除基于垃圾回收器状态和弱引用规则的对象 14 15 size:最大缓存对象或集合 16 flushInterval:缓存刷新间隔,60秒 17 readOnly:缓存是否为只读 18 --> 19 <cache eviction="FIFO" size="512" flushInterval="60000" readOnly="false"></cache> 20 21 22 <!-- SQL引用 --> 23 <sql id="column">id,age,name</sql> 24 25 <!-- 26 查询标签 27 2、id为标签的唯一标识 28 3、parameterType为参数类型 29 4、resultType为返回结果类型 30 31 注意:include的refid为要引用的SQL标签的ID 32 --> 33 <select id="queryUser" parameterType="int" resultType="demo.modul.User" > 34 select <include refid="column"></include> from user where id=#{id} 35 </select> 36 37 <!-- 38 以下演示基本的：插入标签、更新标签、删除标签 39 1、parameterType 参数类型,可以为基本数据类型，也可以为定义的对象 40 2、useGeneratedKeys 是否为自动生成主键 41 3、keyProperty 数据库主键对应的实体类的属性名 42 43 注意：若数据库不支持主键，则可以使用selectKey生成主键 44 --> 45 <insert id="insertUser" parameterType="demo.modul.User" useGeneratedKeys="true" keyProperty="id"> 46 insert into user(name,age) values(#{name},#{age}) 47 </insert> 48 49 50 <update id="updateUser" parameterType="demo.modul.User" > 51 update user set age=#{age} where name=#{name} 52 </update> 53 54 <delete id="deleteUser" parameterType="int"> 55 delete from user where id=#{id} 56 </delete> 57 58 59 60 <!-- 61 MyBatis动态元素演示1： if条件语句 62 --> 63 <select id="testIf" parameterType="demo.modul.User" resultType="demo.modul.User"> 64 select <include refid="column"></include> from user 65 <where> 66 <if test="name!=null"> name like ‘%‘ #{name} ‘%‘</if> 67 </where> 68 </select> 69 70 <!-- 71 MyBatis动态元素演示2： choose分支结构 72 --> 73 <select id="testChoose" parameterType="demo.modul.User" resultType="demo.modul.User"> 74 select <include refid="column"></include> from user WHERE 1=1 75 <choose> 76 <when test="name!=null"> AND name like ‘%‘ #{name} ‘%‘</when> 77 <when test="age!=null"> AND age>#{age}</when> 78 <otherwise>AND id=9</otherwise> 79 </choose> limit 0,1 80 </select> 81 82 <!-- 83 MyBatis动态元素演示3： foreach遍历 84 --> 85 <delete id="testForeach" parameterType="java.util.List" > 86 delete from user where id in 87 <foreach collection="list" item="item" index="index" open="(" close=")" separator=","> 88 #{item} 89 </foreach> 90 </delete> 91 92 <!-- 93 MyBatis动态元素演示4： where 94 注意： 95 1、当第一个if条件不成立时，mybatis会自动去除第一个条件的AND连接符 96 2、只有有任何一条条件成立，则自动添加WHERE关键字 97 --> 98 <select id="testWhere" parameterType="demo.modul.User" resultType="demo.modul.User"> 99 select <include refid="column"></include> from user 100 <where> 101 <if test="name!=null">name like ‘%‘ #{name} ‘%‘</if> 102 <if test="age!=null">AND age >10</if> 103 </where> 104 </select> 105 106 <!-- 107 MyBatis动态元素演示5： set 108 --> 109 <update id="testSet" parameterType="demo.modul.User"> 110 update user 111 <set> 112 <if test="name!=null">name = #{name},</if> 113 <if test="age!=null">age = #{age}</if> 114 </set> 115 where id=#{id} 116 </update> 117 118 119 </mapper>
demo/mybatis/base/mapper/IUser.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"> <!-- 唯一命名空间，必须定义为：所在包名+接口文件名 --> <mapper namespace="demo.mybatis.base.IUser"> <!-- SQL引用 --> <sql id="column">id,age,name</sql> <!-- 查询标签 2、id为标签的唯一标识 3、parameterType为参数类型 4、resultType为返回结果类型 注意:include的refid为要引用的SQL标签的ID --> <select id="getUser" parameterType="int" resultType="demo.modul.User" > select <include refid="column"></include> from user where id=#{id} </select> <select id="getAllUser" parameterType="int" resultType="demo.modul.User" > select <include refid="column"></include> from user where age>#{age} </select> </mapper>
demo/mybatis/base/mapper/IRelate.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"> <!-- 唯一命名空间，必须定义为：所在包名+接口文件名 --> <mapper namespace="demo.mybatis.base.IRelate"> <!-- 演示1：嵌套查询、多对一的关系 注意：此方式存在N+1性能的问题，意思就是每行记录对应的记录都会生产一个子查询 类似于这样的SQL: SELECT table1.id,table1.name,(select sum(table2.age) from table2 where table2.name = table1.name) from table1 --> <resultMap type="demo.modul.Sale" id="userMap"> <id property="id" column="id"/> <result property="name" column="sale_name"/> <result property="age" column="sale_age"/> <association property="user" column="user_id" select="queryOneUser" javaType="demo.modul.User"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="age" column="age"/> </association> </resultMap> <select id="queryOneUser" parameterType="int" resultType="demo.modul.User" > select id,name,age from user where user_id = #{user_id} </select> <select id="querySale" parameterType="int" resultMap="userMap"> select id,sale_name,sale_age,user_id from sale where id = 1 </select> <!-- 演示2：嵌套结果、多对一的关系 注意：解决N+1的SQL查询性能问题 --> <resultMap type="demo.modul.Sale" id="userMap1"> <id property="id" column="sale_id"/> <result property="name" column="sale_name"/> <result property="age" column="sale_age"/> <association property="user" resultMap="userResult" /> </resultMap> <resultMap type="demo.modul.User" id="userResult" > <result property="name" column="user_name"/> <result property="age" column="user_age"/> </resultMap> <select id="querySale1" parameterType="int" resultMap="userMap1"> SELECT sale.id as sale_id,sale_age,sale_name,age as user_age,`name` as user_name FROM sale LEFT JOIN `user` on sale.user_id=user.id WHERE sale.id= #{id} </select> <!-- 演示3：嵌套查询、多对多的关系 注意：存在N+1的SQL查询性能问题 --> <resultMap type="demo.modul.User" id="userQuery"> <result property="name" column="name"/> <result property="age" column="age"/> <result property="userId" column="user_id"/> <collection property="sale" column="user_id" javaType="ArrayList" ofType="demo.modul.Sale" select="querySaleList"> <result property="name" column="name"/> <result property="age" column="age"/> </collection> </resultMap> <select id="querySaleList" resultType="demo.modul.Sale"> SELECT sale_name as name,sale_age as age FROM sale WHERE user_id=#{user_id} </select> <select id="queryUser" parameterType="int" resultMap="userQuery"> SELECT name,age,user_id FROM user WHERE user_id=#{user_id} </select> <!-- 演示3：嵌套结果、多对多的关系 注意：不存在N+1的SQL查询性能问题 --> <resultMap type="demo.modul.User" id="userQuery1"> <result property="name" column="name"/> <result property="age" column="age"/> <result property="userId" column="user_id"/> <collection property="sale" ofType="demo.modul.Sale" columnPrefix="c_" > <result property="name" column="sale_name"/> <result property="age" column="sale_age"/> </collection> </resultMap> <select id="queryUser1" parameterType="int" resultMap="userQuery1"> SELECT user.name,user.age,user.user_id,sale.sale_name as c_sale_name,sale.sale_age as c_sale_age FROM user left join sale on user.user_id = sale.user_id WHERE user.user_id=#{user_id} </select> </mapper>
JAVA接口定义
demo.mybatis.base.IUser
package demo.mybatis.base; import java.util.List; import demo.modul.User; public interface IUser { //获取某个用户 public User getUser(int id); //获取多个用户 public List<User> getAllUser(int age); }
demo.mybatis.base.IRelate
package demo.mybatis.base; import demo.modul.Sale; import demo.modul.User; public interface IRelate { //嵌套查询、多对一 public Sale querySale(int id); //嵌套结果、多对多 public Sale querySale1(int id); //嵌套查询、一对多 public User queryUser(int id); //嵌套结果、一对多 public User queryUser1(int id); }
javabean
demo.modul.User
package demo.modul; import java.util.List; public class User { private int id; private String name; private int age; private List<Sale> sale; private int userId; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public List<Sale> getSale() { return sale; } public void setSale(List<Sale> sale) { this.sale = sale; } public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } }
demo.modul.Sale
package demo.modul; public class Sale { private int id; private int age; private String name; private User user; private int userId; public int getId() { return id; } public void setId(int id) { this.id = id; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } }
测试：
package demo.modul; import java.io.InputStream; import java.util.ArrayList; import java.util.List; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import demo.mybatis.base.IRelate; import demo.mybatis.base.IUser; public class test { public static void main(String[] args) { //mybatis的配置文件 String resource = "conf.xml"; //使用类加载器加载mybatis的配置文件（它也加载关联的映射文件） InputStream is = test.class.getClassLoader().getResourceAsStream(resource); //构建SqlSession的工厂 SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is); //创建能执行映射文件中sql的SqlSession SqlSession session = sessionFactory.openSession(); //执行SQL getRelateUserQuery1(session); } /****************************** 增删改查测试 *********************************/ //查询用户 private static void queryUser(SqlSession session) { //配置文件 命名空间+标签ID String statement = "demo.mybatis.base.mapper.User.queryUser"; //执行查询，并根据配置文件返回结果到对象 User user = session.selectOne(statement,2); //数据输出 System.out.println("ID："+user.getId()); System.out.println("姓名："+user.getName()); System.out.println("年龄："+user.getAge()); } //插入用户 private static void insertUser(SqlSession session) { //参数设置 User u = new User(); u.setAge(15); u.setName("测试插入"); //配置文件对应的命名空间+标签ID String statement = "demo.mybatis.base.mapper.User.insertUser"; //解析SQL并替换参数 int cnt = session.insert(statement, u); //提交SQL session.commit(); //返回结果 System.out.println("受影响行数:"+cnt); } //删除用户 private static void deleteUser(SqlSession session) { //命名空间+标签ID String statement = "demo.mybatis.base.mapper.User.deleteUser"; //解析并执行SQL int cnt = session.update(statement, 6); //提交SQL session.commit(); //结果 System.out.println("受影响行数"); } //更新用户 private static void updateUser(SqlSession session) { //设置参数 User u = new User(); u.setName("测试插入"); u.setAge(26); //命名空间+标签ID String statement = "demo.mybatis.base.mapper.User.updateUser"; //解析SQL并替换参数 int cnt = session.insert(statement,u); //提交参数SQL session.commit(); //返回结果 System.out.println("受影响行数:"+cnt); } /********************* 条件测试 **************************/ //测试IF条件 private static void testIf(SqlSession session) { User condition = new User(); condition.setAge(2); condition.setName("楷"); String statement = "demo.mybatis.base.mapper.User.testIf"; User u = session.selectOne(statement, condition); System.out.println("年龄:"+u.getAge()+" 姓名:"+u.getName()+" ID:"+u.getId()); } //测试choose分支结构 private static void testChoose(SqlSession session) { User condition = new User(); condition.setName("楷"); String statement = "demo.mybatis.base.mapper.User.testChoose"; User u = session.selectOne(statement, condition); System.out.println("年龄:"+u.getAge()+" 姓名:"+u.getName()+" ID:"+u.getId()); } //测试foreach遍历 private static void testForeach(SqlSession session) { List<Integer> list = new ArrayList<Integer>(); list.add(1); list.add(2); list.add(3); list.add(4); //命名空间+标签ID String statement = "demo.mybatis.base.mapper.User.testForeach"; //解析并执行SQL int cnt = session.update(statement, list); //提交SQL session.commit(); //结果 System.out.println("受影响行数"+cnt); } //测试where条件 private static void testWhere(SqlSession session) { User condition = new User(); condition.setName("楷"); String statement = "demo.mybatis.base.mapper.User.testWhere"; User u = session.selectOne(statement, condition); System.out.println("年龄:"+u.getAge()+" 姓名:"+u.getName()+" ID:"+u.getId()); } //测试set条件 private static void testSet(SqlSession session) { User condition = new User(); condition.setName("楷"); condition.setId(1); String statement = "demo.mybatis.base.mapper.User.testSet"; int cnt = session.update(statement, condition); System.out.println("受影响的行数:"+cnt); } /***接口式映射测试***/ //查询某个用户 private static void getUser(SqlSession session) { try { System.out.println(IUser.class); IUser cp = session.getMapper(IUser.class); User u = cp.getUser(2); if (null == u) { System.out.println("没有符合条件的记录"); } else { System.out.println("年龄"+u.getAge()); System.out.println("姓名"+u.getName()); System.out.println("ID"+u.getId()); } } finally { session.close(); } } // 查询多个用户用户 private static void getAllUser(SqlSession session) { try { IUser cp = session.getMapper(IUser.class); List<User> users = cp.getAllUser(2); if (users.size()==0) { System.out.println("没有符合条件的记录"); } else { for(User u:users) { System.out.println("年龄:"+u.getAge()+" 姓名:"+u.getName()+" ID:"+u.getId()); } } } finally { session.close(); } } /************************关联查询*****************************/ //关联查询测试，嵌套查询，多对一关系，存在N+1的SQL性能问题 private static void getRelateQuery(SqlSession session) { IRelate relate = session.getMapper(IRelate.class); Sale sale = relate.querySale(1); System.out.println("业务姓名:"+sale.getName()+" 业务年龄:"+sale.getAge()+" 业务id:"+sale.getId()+ " 客户姓名:"+sale.getUser().getName()+" 客户年龄:"+sale.getUser().getAge()); } //关联查询测试，嵌套结果，多对一关系 ，解决N+1的SQL性能问题 private static void getRelateQuery1(SqlSession session) { IRelate relate = session.getMapper(IRelate.class); Sale sale = relate.querySale1(1); System.out.println("业务姓名:"+sale.getName()+" 业务年龄:"+sale.getAge()+" 业务id:"+sale.getId()+ " 客户姓名:"+sale.getUser().getName()+" 客户年龄:"+sale.getUser().getAge()); } //关联查询集合，嵌套查询，多对多关系，存在N+1的性能问题 private static void getRelateUserQuery(SqlSession session) { IRelate relate = session.getMapper(IRelate.class); User user = relate.queryUser(5); System.out.println("姓名:"+user.getName()+" 年龄:"+user.getAge()+" 用户ID:"+user.getUserId()); for(Sale s:user.getSale()) { System.out.println("销售名称:"+s.getName()+" 销售年龄:"+s.getAge()); } } //关联查询集合，嵌套结果，多对多关系，解决N+1的性能问题 private static void getRelateUserQuery1(SqlSession session) { IRelate relate = session.getMapper(IRelate.class); User user = relate.queryUser1(5); System.out.println("姓名:"+user.getName()+" 年龄:"+user.getAge()+" 用户ID:"+user.getUserId()); for(Sale s:user.getSale()) { System.out.println("销售名称:"+s.getName()+" 销售年龄:"+s.getAge()); } } }
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原文地址：http://www.cnblogs.com/curen/p/5942583.html
