Mybatis简单使用+拦截器分页
当前环境：JDK:1.8 Maven项目
https://mybatis.org/mybatis-3/zh/
一、mybatis 简单使用
1、在pom.xml中添加依赖包
<dependencies>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.6</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.22</version>
</dependency>
<!--Test-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.1</version>
<scope>test</scope>
</dependency>
</dependencies>
2、在application.properties中配置数据连接
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost/temp_db?serverTimezone=Asia/Shanghai&useSSL=false&useUnicode=true&characterEncoding=utf-8
username=root
password=123456
3、创建dao中的接口（添加，查询全部，分页查询）
public interface StudentDao {
void addStudent(@Param("stu") Student student);
List<Student> queryList();
List<Student> queryByPage(@Param("page") Page<Student> page);
}
4、创建mybatis要映射的xml文件（没有和dao发在一起，发在了resources->mybatis文件夹下）
Tis:注意namespace地址的正确
分页查询的sql语句不要加分号；，在拼接sql查询总数时会出错，去掉就行了，或者在改拦截器把这里的；截取掉
<?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.liang.dao.StudentDao">
<insert id="addStudent" useGeneratedKeys="true" keyProperty="id">
insert into t_student(id,name,sex,schoolId,create_time,update_time) values(#{stu.id},#{stu.name},#{stu.sex},#{stu.schoolId},#{stu.create_Time},#{stu.update_Time});
</insert>
<select id="queryList" resultType="cn.liang.pojo.Student">
select * from t_student;
</select>
<select id="queryByPage" resultType="cn.liang.pojo.Student">
select * from t_student
</select>
</mapper>
5、添加分页拦截器（mybatis支持插件）
package cn.liang.config;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import java.awt.geom.Area;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Map;
import java.util.Properties;
/**
* @Intercepts 说明是一个拦截器
*/
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class MyPageInterceptor implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
MetaObject metaObject = MetaObject.forObject(statementHandler,
SystemMetaObject.DEFAULT_OBJECT_FACTORY, SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY,
new DefaultReflectorFactory());
MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
String id = mappedStatement.getId();
//需要方法名称以Page结尾
if (id.endsWith("Page")){
BoundSql boundSql = statementHandler.getBoundSql();
Map<String, Object> map = (Map<String, Object>) boundSql.getParameterObject();
//需要在具体查询方法Page参数前添加@Param("page")
Page<Area> page = (Page<Area>) map.get("page");
String sql = boundSql.getSql();
String countSql = "select count(*) from (" + sql + ") a";//PS:注意查询sql不要带分号；不然在下面组合sql时报错
Connection connection = (Connection) invocation.getArgs()[0];
PreparedStatement preparedStatement = connection.prepareStatement(countSql);
ParameterHandler parameterHandler = (ParameterHandler) metaObject.getValue("delegate.parameterHandler");
parameterHandler.setParameters(preparedStatement);
ResultSet rs = preparedStatement.executeQuery();
if (rs.next()){
page.setTotalPage(rs.getInt(1));
}
String pageSql = sql + " limit " + (page.getIndexPage()-1)*page.getPageSize() + ", " + page.getPageSize();
metaObject.setValue("delegate.boundSql.sql", pageSql);
}
return invocation.proceed();
}
//获取代理对象
@Override
public Object plugin(Object o) {
//生成object对象的动态代理对象
return Plugin.wrap(o,this);
}
//设置代理对象的参数
@Override
public void setProperties(Properties properties) {
}
}
public class Page<T> implements Serializable {
private static final long serialVersionUID = 1L;
private Integer totalPage;
private Integer pageSize = 10;
private Integer indexPage = 1;
private List<T> dataList;
public Page() {}
public Page(Integer pageSize, Integer indexPage) {
this.pageSize = pageSize;
this.indexPage = indexPage;
}
public Integer getTotalPage() {
return totalPage;
}
public void setTotalPage(Integer totalPage) {
this.totalPage = totalPage;
}
public Integer getPageSize() {
return pageSize;
}
public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}
public Integer getIndexPage() {
return indexPage;
}
public void setIndexPage(Integer indexPage) {
this.indexPage = indexPage;
}
public List<T> getDataList() {
return dataList;
}
public void setDataList(List<T> dataList) {
this.dataList = dataList;
}
}
6、在resources 文件夹下添加mybatis-config.xml配置文件
<!--配置环境变量、事务和数据源-->
<?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>
<!--读取属性,也可自定义属性（注意位置）-->
<properties resource="application.properties"/>
<!--设置xml中全限定名的别名-->
<typeAliases>
<package name="cn.liang.pojo"/>
</typeAliases>
<!--注册自定义分页拦截器Interceptor-->
<plugins>
<plugin interceptor="cn.liang.config.MyPageInterceptor">
</plugin>
</plugins>
<!--配置环境变量、事务和数据源-->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<!--设置mapper映射的xml路径-->
<mappers>
<!--xml文件发在了resources->mybatis文件夹下-->
<mapper resource="mybatis/StudentMapper.xml" />
</mappers>
</configuration>
7、从 XML 中构建 SqlSessionFactory
package cn.liang.config;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
public static SqlSessionFactory sqlSessionFactory;
static {
String resource="mybatis-config.xml";
try {
InputStream inputStream=Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
}
8、测试执行
public class Mybatis3ApplicationTests {
@Test
public void testMybatisPageList(){
SqlSession session = MybatisUtils.sqlSessionFactory.openSession();
try{
StudentDao mapper = session.getMapper(StudentDao.class);
Page<Student> studentPage = new Page<Student>();
// studentPage.setIndexPage(2);
// studentPage.setPageSize(3);
List<Student> list = mapper.queryByPage(studentPage);
studentPage.setDataList(list);
for (Student student : studentPage.getDataList()) {
System.out.println(student.toString());
}
System.out.println(studentPage.getPageSize());
System.out.println(studentPage.getTotalPage());
}
finally {
session.close();
}
}
@Test
public void testMybatisList(){
SqlSession session = MybatisUtils.sqlSessionFactory.openSession();
try{
StudentDao mapper = session.getMapper(StudentDao.class);
List<Student> list = mapper.queryList();
for (Student student : list) {
System.out.println(student.toString());
}
}
finally {
session.close();
}
}
@Test
public void testMybatis() throws SQLException {
SqlSession session = MybatisUtils.sqlSessionFactory.openSession();
try {
StudentDao mapper = session.getMapper(StudentDao.class);
Student student = new Student("带老大2", "男", 1);
mapper.addStudent(student);
System.out.println(student.getId());
session.commit();
} finally {
session.close();
}
}
}
项目目录结构
如果出现一下错误，请修改文件编码格式
Caused by: com.sun.org.apache.xerces.internal.impl.io.MalformedByteSequenceException: 1 字节的 UTF-8 序列的字节 1 无效
