Mybatis基础
mybatis
mybatis-config.xml详细配置
<configuration>
<properties>properties>
<settings>
<setting name="" value=""/>
settings>
<typeAliases>
<typeAlias type="包路径" alias="别名">typeAlias>
<package name="包名"/>
typeAliases>
<typeHandlers>typeHandlers>
<objectFactory type="">objectFactory>
<plugins>
<plugin interceptor="">plugin>
plugins>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url"
value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=GMT%2B8&useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
<property name="password" value="123"/>
<property name="username" value="root"/>
dataSource>
environment>
environments>
<databaseIdProvider type="">databaseIdProvider>
<mappers>
<mapper resource="com/kang/w/dao/impl/UserMapper.xml">mapper>
mappers>
configuration>
分页
减少数据访问量
limt实现分页
sql语句: select * from 表名 limt 0,5;
- 0:数据开始的位置
- 5:数据的长度
第一种:使用Mybatis
1接口
List<User> getUserByLimit(Map<String, Object> map);
2mapeer.xml
<select id="getUserByLimit" parameterType="map" resultType="user">
select *
from mybatis.user
limit ${starIndex},${pageSize}
select>
2-1结果集映射
<resultMap id="map" type="User">
<result property="pwd" column="password">result>
resultMap>
3测试
@Test
public void getUserByLimitTest() {
SqlSession sqlSession = MyBatisUtils.getSqlSession ();
UserMapper mapper = sqlSession.getMapper (UserMapper.class);
HashMap hashMap = new HashMap<String, Object> ();
hashMap.put ("starIndex", 1);
hashMap.put ("pageSize", 2);
List userByLimit = mapper.getUserByLimit (hashMap);
for (Object o : userByLimit) {
System.out.println (o);
}
sqlSession.close ();
}
第二种：使用RowBounds方法
1.接口
List getUserList();
2.实现接口
<select id="getUserList" resultType="user">
select *
from mybatis.user
select>
3.测试：
/**
* 测试使用RowBounds实现分页
*/
@Test
public void getUserByLimitRowBoundsTest() {
SqlSession sqlSession = MyBatisUtils.getSqlSession ();
RowBounds rowBounds = new RowBounds (0, 2);
List<User> userList = sqlSession.selectList ("com.kuang.w.dao.UserMapper.getUserList", null, rowBounds);
for (User user : userList) {
System.out.println (user);
}
//关闭
sqlSession.close ();
}
第三种：使用Mybatis的分页插件 pageHeIper
sql 多对一处理
数据库 ：
pojo
数据库中teacher-table表 对应实体类 Teacher
package com.kuang.w.pojo;
import lombok.Data;
/**
* @author W
*/
@Data
public class Teacher {
private int tId;
private String tName;
}
数据库中user表 对应 实体类Student
package com.kuang.w.pojo;
import lombok.Data;
/**
* @author W
*/
@Data
public class Student {
private int id;
private int tid;
private String name;
private String password;
private Teacher teacher;
}
1.接口
List<Student> getStudentList();
2.xml配置实现接口
<select id="getStudentList" resultMap="studentTeacher">
select *
from mybatis.user;
select>
<resultMap id="studentTeacher" type="Student">
<result property="id" column="id"/>
<result property="name" column="name"/>
<result property="password" column="password"/>
<association property="teacher" column="tid" javaType="Teacher" select="getTeacher">association>
resultMap>
<select id="getTeacher" resultType="Teacher">
select *
from mybatis.teacher_table
where tid = #{id};
select>
<select id="getStudentList" resultMap="StudentList">
select u.id uid,
u.name uname,
u.password upassword,
u.tid utid,
t.tname
from mybatis.user u,
mybatis.teacher_table t
where t.tid = u.tid;
select>
<resultMap id="StudentList" type="Student">
<result column="uid" property="id"/>
<result column="utid" property="tid"/>
<result column="uname" property="name"/>
<result column="upassword" property="password"/>
<association property="teacher" javaType="Teacher">
<result property="tName" column="tname">result>
association>
resultMap>
mybatis-config.xm配置
<configuration>
<properties resource="db.properties"/>
<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
settings>
<typeAliases>
<typeAlias type="com.kuang.w.pojo.Teacher" alias="teacher"/>
<typeAlias type="com.kuang.w.pojo.Student" alias="student"/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="password" value="${password}"/>
<property name="username" value="${username}"/>
dataSource>
environment>
environments>
<mappers>
<mapper class="com.kuang.w.dao.StudentMapper">mapper>
<mapper class="com.kuang.w.dao.TeacherMapper">mapper>
mappers>
configuration>
3 测试
@Test
public void getStudentListTest() {
SqlSession sqlSession = MyBatisUtils.getSqlSession ();
StudentMapper mapper = sqlSession.getMapper (StudentMapper.class);
List<Student> studentList = mapper.getStudentList ();
for (Student student : studentList) {
System.out.println (student);
}
sqlSession.commit ();
sqlSession.close ();
}
sql 一对多处理
数据表结构 对应的实体类 不变
第一种方式： 多表联查
1接口
List<Teacher> getTeacher(int tid);
2.1 xml实现接口
<select id="getTeacher" resultMap="TeacherStudent">
select t.tid, t.tname, u.id, u.name, u.password
from mybatis.user u,
mybatis.teacher_table t
where t.tid = u.tid
and t.tid = #{tid};
select>
2.2映射配置
<resultMap id="TeacherStudent" type="Teacher">
<result property="tName" column="tname"/>
<result property="tId" column="tid"/>
<collection property="students" ofType="Student">
<result column="id" property="id">result>
<result column="name" property="name">result>
<result column="password" property="password">result>
<result column="tid" property="tid">result>
collection>
resultMap>
3测试
/*测试一对多*/
@Test
public void getTeacherTest2() {
SqlSession sqlSession = MyBatisUtils.getSqlSession ();
TeacherMapper mapper = sqlSession.getMapper (TeacherMapper.class);
List<Teacher> teacher = mapper.getTeacher (1);
for (Teacher teacher1 : teacher) {
System.out.println (teacher1);
}
//提交事务 架子 这里可以不要
sqlSession.commit ();
// 关闭
sqlSession.close ();
}
结果
com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.kuang.w.dao.myTest,getTeacherTest2
Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
Opening JDBC Connection
Created connection 164974746.
Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@9d5509a]
==> Preparing: select t.tid, t.tname, u.id, u.name, u.password from mybatis.user u, mybatis.teacher_table t where t.tid = u.tid and t.tid = ?;
==> Parameters: 1(Integer)
<== Columns: tid, tname, id, name, password
<== Row: 1, 狂神, 1, 天王盖地虎, 111
<== Row: 1, 狂神, 2, 小波, 123
<== Row: 1, 狂神, 3, 雷神, 922
<== Row: 1, 狂神, 5, 马儿扎哈, 123
<== Total: 4
Teacher(tId=1, tName=狂神, students=[Student(id=1, tid=1, name=天王盖地虎, password=111), Student(id=2, tid=1, name=小波, password=123), Student(id=3, tid=1, name=雷神, password=922), Student(id=5, tid=1, name=马儿扎哈, password=123)])
Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@9d5509a]
Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@9d5509a]
Returned connection 164974746 to pool.
Process finished with exit code 0
第二种方式： 子查询
1接口
List<Teacher> getTeacher(int tid);
2 实现接口
<select id="getTeacher3" resultMap="TeacherStudent3">
select *
from mybatis.teacher_table
where tid = #{tid};
select>
<resultMap id="TeacherStudent3" type="Teacher">
<result column="tid" property="tId"/>
<result column="tname" property="tName"/>
<collection property="students" javaType="ArrayList" ofType="Student" select="getStudentByTeacherId"
column="tid">
collection>
resultMap>
<select id="getStudentByTeacherId" resultType="Student">
select *
from mybatis.user
where tid = #{tid};
select>
3测试 同上
。。。。