2、搭建Java工程
A、加入mybatis核心包、依赖包、数据驱动包
B、在classpath下创建log4j.properties和db.propertites（mybatis默认使用log4j作为输出日志信息）
log4j.properties
# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# 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%ndb.propertites
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8
jdbc.username=root
jdbc.password=rootC、在classpath下创建SqlMapConfig.xml
<?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>
<!-- 加载数据库驱动信息 -->
<properties resource="db.properties"></properties>
<!-- 配置别名 -->
<typeAliases>
<!--扫描包的形式创建别名，别名就是类名，不区分大小写 -->
<package name="com.kid.mybatis.pojo"/>
</typeAliases>
<!-- 和spring整合后 environments配置将废除-->
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理-->
<transactionManager type="JDBC"/>
<!-- 数据库连接池-->
<dataSource type="POOLED">
<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>
<!-- 加载mapper文件 -->
<mappers>
<!-- 使用扫描包的形式加载mapper文件 -->
<package name="com.kid.mybatis.mapper"/>
</mappers>
</configuration>D、pojo类
public class Orders {
private Integer id;
private Integer userId;
private String number;
private Date createtime;
private String note;
private User user;
//省略getter/setter方法
}
public class QueryVo {
private User user;
private List<Integer> ids;
省略getter/setter方法
｝
public class User {
private Integer id;
private String username;
private String sex;
private Date birthday;
private String address;
省略getter/setter方法
｝3、输入映射和输出映射：resultType和resultMap的使用
OrderMapper接口：
public interface OrderMapper {
List<Orders> getOrderList();
List<Orders> getOrderListResultMap();
}
OrderMapper.xml：
<mapper namespace="com.kid.mybatis.mapper.OrderMapper">
<select id="getOrderList" resultType="orders">
select id,user_id userId,number,createtime,note from orders
</select>
<!--使用resultMap; type:返回结果映射的pojo,可以使用别名-->
<resultMap type="orders" id="order_list_result_map">
<!--id主键的映射，property是pojo中主键的属性，column:返回结果中主键映射 -->
<id property="id" column="id"/>
<result property="userId" column="user_id"/>
<result property="number" column="number"/>
<result property="createtime" column="createtime"/>
<result property="note" column="note"/>
</resultMap>
<select id="getOrderListResultMap" resultMap="order_list_result_map">
select id,user_id,number,createtime,note from orders
</select>
</mapper>
测试文件：OrderMapperTest
public class OrderMapperTest {
private SqlSessionFactory sqlSessionFactory = null;
@Before
public void init() throws Exception {
//第一步：创建一个SQLSessionFactoryBuilder对象。
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
//第二步：加载配置文件。
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
//第三步：创建SQLSessionFactory对象
sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
}
@Test
public void getOrderList() {
SqlSession sqlSession = sqlSessionFactory.openSession();
OrderMapper orderMapper = sqlSession.getMapper(OrderMapper.class);
List<Orders> orderList = orderMapper.getOrderList();
for (Orders orders : orderList) {
System.out.println(orders);
}
sqlSession.close();
}
@Test
public void getOrderListResultMap() {
SqlSession sqlSession = sqlSessionFactory.openSession();
OrderMapper orderMapper = sqlSession.getMapper(OrderMapper.class);
List<Orders> orderList = orderMapper.getOrderList();
for (Orders orders : orderList) {
System.out.println(orders);
}
sqlSession.close();
}
}这一块主要讲输入和输出映射无法匹配的问题！我们的 Order 中是userId,数据库中的字段名称是 user_id，这块我们使用了2种方法查询：
A、别名查询 select id,user_id userId,number,createtime,note from orders
B、使用 requltMap ,type:返回结果映射的pojo,可以使用别名(详细看上面注释)
resultMap标签简单介绍：
<id />：此属性表示查询结果集的唯一标识，非常重要。如果是多个字段为复合唯一约束则定义多个<id />。
Property：表示User类的属性。
Column：表示sql查询出来的字段名。
Column 和 property放在一块儿表示将sql查询出来的字段映射到指定的pojo类属性上。
<result />：普通结果，即pojo的属性。4、动态SQL语句
UserMapper接口：
public interface UserMapper {
User getUserByQueryVo(QueryVo queryVo);
int findUserCount();
List<User> findUserList(User user);
List<User> findUseListByIds(QueryVo queryVo);
}
UserMapper.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.kid.mybatis.mapper.UserMapper">
<!-- 通过queryVo查询客户 -->
<select id="getUserByQueryVo" parameterType="queryvo" resultType="user">
select * from user where id = #{user.id}
</select>
<!-- 查询用户总数 -->
<select id="findUserCount" resultType="int">
select count(*) from user
</select>
<!-- ############################# 华丽的 分割线 ################################# -->
<!-- SQL片段引用&传递pojo综合查询用户信息 -->
<sql id="find_user_list_where">
<where>
<if test="id != null">
and id =#{id}
</if>
<if test="username != null and username != ‘‘ ">
and username like ‘%${username}%‘
</if>
</where>
</sql>
<select id="findUserList" parameterType="user" resultType="user">
select * from user
<include refid="find_user_list_where"/>
</select>
<!-- ############################# 华丽的 分割线 ################################# -->
<!-- SQL片段 & 动态sql foreach语句 -->
<sql id="user_field_list">
id,username,birthday,sex,address
</sql>
<select id="findUseListByIds" parameterType="queryvo" resultType="user">
select <include refid="user_field_list"/>
from user
<where>
<foreach collection="ids" item="id" open="and id in(" close=")" separator=",">
#{id}
</foreach>
</where>
</select>
</mapper>
测试文件 UserMapperTest:
public class UserMapperTest {
private SqlSessionFactory sqlSessionFactory = null;
@Before
public void init() throws Exception {
//第一步：创建一个SQLSessionFactoryBuilder对象。
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
//第二步：加载配置文件。
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
//第三步：创建SQLSessionFactory对象
sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
}
@Test
public void findUserByQueryVoTest() {
SqlSession sqlSession = sqlSessionFactory.openSession();
//获取mapper的代理对象
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//创建QueryVo对象
QueryVo queryVo=new QueryVo();
//创建User对象
User user=new User();
user.setId(10);
queryVo.setUser(user);
//根据queryvo查询客户
User u = userMapper.getUserByQueryVo(queryVo);
System.out.println(u);
sqlSession.close();
}
@Test
public void findUserCountTest() {
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
int count = userMapper.findUserCount();
sqlSession.close();
System.out.println(count);
}
@Test //动态Sql测试
public void findUserListTest() {
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
User user=new User();
user.setId(10);
user.setUsername("张");
List<User> userList = userMapper.findUserList(user);
//循环遍历
for (User user2 : userList) {
System.out.println(user2);
}
sqlSession.close();
}
@Test //动态Sql测试
public void findUseListByIdsTest() {
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
QueryVo queryVo=new QueryVo();
List<Integer> ids = new ArrayList<>();
ids.add(1);//查询id为1的用户
ids.add(10); //查询id为10的用户
queryVo.setIds(ids);
List<User> userList = userMapper.findUseListByIds(queryVo);
//循环遍历
for (User user2 : userList) {
System.out.println(user2);
}
sqlSession.close();
}
}
项目结构图
原文地址：https://www.cnblogs.com/miantiao312/p/9649486.html
时间： 2024-08-24 10:51:03