标签：href xml配置 增加 -- and 方案 err one 行数据
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映射文件：
主要是在xxxmapper.xml文件里的配置
映射文件指导这MyBatis如何进行数据库的增删该查，有着很重要的意义。
下面开始进入正题，最后会发一个完整版的代码
因为实现的主要内容是增删改查，所以我们现在接口类中定义好相关的方法，后面不在进行单一的定义！
工程的目录如下：
EmployeeMapper.java
package com.MrChengs.dao; import java.util.Map; import org.apache.ibatis.annotations.Param; import org.apache.ibatis.annotations.Select; import com.MrChengs.bean.Employee; public interface EmployeeMapper {
//我们直接传入map public Employee getByMap(Map<String,Object> map); //查询满足两个条件的数据 public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name); //查询 public Employee getEmployee(int id); //增加 public void addEmp(Employee employee); //更新 public void updateEmp(Employee employee); //删除 public void deleteById(int id); }
1）insert-映射插入语句
1.1）EmployeeMapper.xml
<insert id="addEmp" >
insert into test(name,gender,email) values(#{name},#{gender},#{email})
</insert>
@Test public void test2() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手动添加数据： Employee em = new Employee( "zhangsan", "boy", "zhangsan@qq.com"); mapper.addEmp(em); //手动提交数据 sqlSession.commit(); }finally{ sqlSession.close(); }}
1.3)测试成功
2）update映射更新语句
2.1）EmployeeMapper.xml
<update id="updateEmp"> update test set name=#{name},gender=#{gender} where id=#{id} </update>
2.2）测试类中
@Test public void test3() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手动添加数据： Employee em = new Employee( 6,"Jerry", "gril", null); mapper.updateEmp(em); //手动提交数据 sqlSession.commit(); }finally{ sqlSession.close();}}
2.3）测试成功！
3）delete-映射删除操作
3.1）EmployeeMapper.xml
<delete id="deleteById"> delete from test where id=#{id} </delete>
3.2）测试类中
@Test public void test4() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手动添加数据： mapper.deleteById(6); //手动提交数据 sqlSession.commit(); }finally{ sqlSession.close();}}
3.3）测试成功！
4）关于主键的值问题
有时候需要用到主键值的问题，所以我们需要去学习这个知识点！
4.1）EmployeeMapper.xml
<!-- useGeneratedKeys="true"使用自增主键获取主键的值 -->
<!-- keyProperty=""接受对应的主键值-->
<insert id="addEmp" useGeneratedKeys="true" keyProperty="id">
insert into test(name,gender,email) values(#{name},#{gender},#{email})
</insert>
4.2)测试类
@Test public void test2() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手动添加数据： Employee em = new Employee( "zhangsan", "boy", "zhangsan@qq.com"); mapper.addEmp(em); //获取主键值的属性值进行打印 System.out.println(em.getId()); //手动提交数据 sqlSession.commit(); }finally{ sqlSession.close(); } }
4.3）测试成功
5）参数处理
5.1）单个参数：MyBatis不会做任何处理
#{参数名} ： 取出参数值
5.1.1）xml配置文件中
<select id="getId" resultType="com.MrChengs.bean.Employee"> select id,name,gender,email from test where id = #{idabc} </select>
5.1.2）测试类
@Test public void test() throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = (SqlSessionFactory) new SqlSessionFactoryBuilder().build(inputStream); SqlSession session = sqlSessionFactory.openSession(); try{ Employee employee = session.selectOne("getId",5); System.out.println(employee); }finally{ session.close(); } }
5.1.3）测试是成功的！
5.2）多个参数时
MyBatis会做特殊的处理
多个参数时封装成map
key param1 ,param2......
value 传入的值
5.2.1）接口类中的查询代码设计如上所展示的
public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name);
此时去掉@param：
public Employee getByIdAndNames(int id,String name);
5.2.2) xml文件
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
5.2.3）测试代码
@Test public void test5() throws IOException{ SqlSessionFactory sessionFactory = getSqlSessionFactory(); SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class); Employee employee = mapper.getByIdAndNames(5, "MrChengs"); System.out.println(employee); }finally{ sqlSession.close(); } }
5.2.4）此时会报错
5.2.5）处理方案：是在EmployeeMapper.xml文件中修改的
<!-- 同时使用两个参数进行数据库的查询 -->
<!-- public Employee getByIdAndNames(int id,String name); -->
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" >
select id,name,gender,email from test where id = #{param1}
and name=#{param2}
</select>
此时得到正确的答案！
5.3）多个查询字段时推荐使用的命名字段
public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name);
5.3.2）xml文件中
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
public Employee getByMap(Map<String,Object> map);
5.4.2）xml文件中添加
<select id="getByMap" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
5.4.3）测试类
@Test public void test6() throws IOException{ SqlSessionFactory sessionFactory = getSqlSessionFactory(); SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class); Map<String, Object> map = new HashMap<>(); map.put("id", 5); map.put("name", "MrChengs"); Employee employee = mapper.getByMap(map); System.out.println(employee); }finally{ sqlSession.close(); } }
运行时，可以正确输出结果!
5.5）思考问题注意
标签：href xml配置 增加 -- and 方案 err one 行数据
原文地址：https://www.cnblogs.com/Mrchengs/p/9721608.html
