mybatis-普通sq增删改查学习笔记

 import java.util.*; import cn.mybatis.entity.Student; import cn.mybatis.util.MybatisUtil; import org.apache.ibatis.session.SqlSession; public class StudentDao { /** * 增加学生 */ public void add(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); //事务开始（默认） //读取StudentMapper.xml映射文件中的SQL语句 int i = sqlSession.insert(Student.class.getName()+".add",student); System.out.println("本次操作影响了"+i+"行"); //事务提交 sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); //事务回滚 sqlSession.rollback(); throw e; }finally{ //MybatisUtil.closeSqlSession(); } } /** * 根据ID查询学生 */ public Student findById(int id) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); Student student = sqlSession.selectOne(Student.class.getName()+".findById",id); sqlSession.commit(); return student; }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } /** * 查询所有学生 */ public List<Student> findAll() throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); return sqlSession.selectList(Student.class.getName()+".findAll"); }catch(Exception e){ e.printStackTrace(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } /** * 更新学生 */ public void update(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.update(Student.class.getName()+".update",student); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } /** * 删除学生 */ public void delete(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.delete(Student.class.getName()+".delete",student); //事务 sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); // 回滚 sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception { StudentDao dao = new StudentDao(); // dao.add(new Student(3,"美丽",70030.3)); // dao.add(new Student(4,"加油",70030.3)); // dao.add(new Student(5,"关系",70030.3)); // dao.add(new Student(6,"规律",70030.3)); // dao.add(new Student(7,"古蔺",70030.3)); // List<Student> studentslist = dao.findAll(); // for (Student student : studentslist ) { // System.out.print(student.getId()+":"+student.getName()+":"+student.getSal()); // } // Student student = dao.findById(4); // student.setName("liwen"); // dao.update(student); } } 

<?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="cn.mybatis.entity.Student"> <resultMap type="cn.mybatis.entity.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <!-- 增加学生 --> <insert id="add" parameterType="cn.mybatis.entity.Student"> insert into students(id,name,sal) values(#{id},#{name},#{sal}) </insert> <!-- 根据ID查询学生 如果参数不是一个实体的话，只是一个普通变量，例如:int,double,String 这里的#{中间的变量名可以随便写}，不过提倡就用方法的形参 --> <select id="findById" parameterType="int" resultType="cn.mybatis.entity.Student"> select id,name,sal from students where id = #{id} </select> <!-- 查询所有学生 理论上resultType要写List<Student> 但这里只需书写List中的类型即可，即只需书写Student的全路径名 --> <select id="findAll" resultType="cn.mybatis.entity.Student"> select id,name,sal from students </select> <!-- 更新学生 --> <update id="update" parameterType="cn.mybatis.entity.Student"> update students set name=#{name},sal=#{sal} where id=#{id} </update> <!-- 删除学生 --> <delete id="delete" parameterType="cn.mybatis.entity.Student"> delete from students where id = #{id} </delete> <!-- 无条件分页 --> <select id="findAllWithFy" parameterType="map" resultMap="studentMap"> select id,name,sal from students limit #{pstart},#{psize} </select>