mysql describe 分页_MyBatis分页

太过爱你忘了你带给我的痛 2023-10-05 18:43 12阅读 0赞

搞清楚什么是分页(pagination)

例如，在数据库的某个表里有1000条数据，我们每次只显示100条数据，在第1页显示第0到第99条，在第2页显示第100到199条，依次类推，这就是分页。

分页可以分为逻辑分页和物理分页。逻辑分页是我们的程序在显示每页的数据时，首先查询得到表中的1000条数据，然后成熟根据当前页的“页码”选出其中的100条数据来显示。

物理分页是程序先判断出该选出这1000条的第几条到第几条，然后数据库根据程序给出的信息查询出程序需要的100条返回给我们的程序。

MyBatis 物理分页

MyBatis使用RowBounds实现的分页是逻辑分页,也就是先把数据记录全部查询出来,然在再根据 offset 和 limit 截断记录返回。

为了在数据库层面上实现物理分页，又不改变原来 MyBatis 的函数逻辑,可以编写 plugin 截获 MyBatis Executor 的 statementhandler，重写SQL来执行查询。

经常搭框架的人应该都清楚，框架搭建的核心就是配置文件。

在这里我们需要创建 web 工程。也需要用 mybatis与Spring mvc 集成起来，源码在本文结尾处下载，主要有以下几个方面的配置。

整个Mybatis分页示例要完成的步骤如下：

1、示例功能描述

2、创建工程

3、数据库表结构及数据记录

4、实例对象

5、配置文件

6、测试执行，输出结果

1、示例功能描述

在本示例中，需要使用 MyBatis和Spring MVC整合完成分页，完成这样的一个简单功能，即指定一个用户(ID=1)，查询出这个用户关联的所有订单分页显示出来(使用的数据库是：MySQL)。

2、创建工程

首先创建一个工程的名称为：mybatis08-paging，在 src 源代码目录下建立文件夹 config，并将原来的 mybatis 配置文件 Configuration.xml 移动到这个文件夹中, 并在 config 文家夹中建立 Spring 配置文件：applicationContext.xml。工程结构目录如下：

![08d8ce07b9b1cee43923479a5c108310.png][]

3、数据库表结构及数据记录

在本示例中，用到两个表：用户表和订单表，其结构和数据记录如下：

CREATE TABLE \`user\` (

\`id\` int(10) unsigned NOT NULL AUTO\_INCREMENT,

\`username\` varchar(64) NOT NULL DEFAULT '',

\`mobile\` varchar(16) NOT NULL DEFAULT '',

PRIMARY KEY (\`id\`)

) ENGINE=InnoDB AUTO\_INCREMENT=3 DEFAULT CHARSET=utf8;

\-- ----------------------------

\-- Records of user

\-- ----------------------------

INSERT INTO \`user\` VALUES ('1', 'yiibai', '13838009988');

INSERT INTO \`user\` VALUES ('2', 'saya', '13838009988');

订单表结构和数据如下：

CREATE TABLE \`order\` (

\`order\_id\` int(10) unsigned NOT NULL AUTO\_INCREMENT,

\`user\_id\` int(10) unsigned NOT NULL DEFAULT '0',

\`order\_no\` varchar(16) NOT NULL DEFAULT '',

\`money\` float(10,2) unsigned DEFAULT '0.00',

PRIMARY KEY (\`order\_id\`)

) ENGINE=InnoDB AUTO\_INCREMENT=17 DEFAULT CHARSET=utf8;

\-- ----------------------------

\-- Records of order

\-- ----------------------------

INSERT INTO \`order\` VALUES ('1', '1', '1509289090', '99.90');

INSERT INTO \`order\` VALUES ('2', '1', '1519289091', '290.80');

INSERT INTO \`order\` VALUES ('3', '1', '1509294321', '919.90');

INSERT INTO \`order\` VALUES ('4', '1', '1601232190', '329.90');

INSERT INTO \`order\` VALUES ('5', '1', '1503457384', '321.00');

INSERT INTO \`order\` VALUES ('6', '1', '1598572382', '342.00');

INSERT INTO \`order\` VALUES ('7', '1', '1500845727', '458.00');

INSERT INTO \`order\` VALUES ('8', '1', '1508458923', '1200.00');

INSERT INTO \`order\` VALUES ('9', '1', '1504538293', '2109.00');

INSERT INTO \`order\` VALUES ('10', '1', '1932428723', '5888.00');

INSERT INTO \`order\` VALUES ('11', '1', '2390423712', '3219.00');

INSERT INTO \`order\` VALUES ('12', '1', '4587923992', '123.00');

INSERT INTO \`order\` VALUES ('13', '1', '4095378812', '421.00');

INSERT INTO \`order\` VALUES ('14', '1', '9423890127', '678.00');

INSERT INTO \`order\` VALUES ('15', '1', '7859213249', '7689.00');

INSERT INTO \`order\` VALUES ('16', '1', '4598450230', '909.20');

4、实例对象

用户表和订单表分别对应两个实例对象，分别是：User.java 和 Order.java，它们都在 com.yiibai.pojo 包中。

User.java代码内容如下：

package com.yiibai.pojo;

import java.util.List;

/\*\*

\* @describe: User

\* @author: Yiibai

\* @version: V1.0

\* @copyright http://www.yiibai.com

\*/

public class User \{

private int id;

private String username;

private String mobile;

public int getId() \{

return id;

public void setId(int id) \{

this.id = id;

public String getUsername() \{

return username;

public void setUsername(String username) \{

this.username = username;

public String getMobile() \{

return mobile;

public void setMobile(String mobile) \{

this.mobile = mobile;

Order.java代码内容如下：

package com.yiibai.pojo;

/\*\*

\* @describe: User - 订单

\* @author: Yiibai

\* @version: V1.0

\* @copyright http://www.yiibai.com

\*/

public class Order \{

private int orderId;

private String orderNo;

private float money;

private int userId;

private User user;

public int getUserId() \{

return userId;

public void setUserId(int userId) \{

this.userId = userId;

public int getOrderId() \{

return orderId;

public void setOrderId(int orderId) \{

this.orderId = orderId;

public User getUser() \{

return user;

public void setUser(User user) \{

this.user = user;

public String getOrderNo() \{

return orderNo;

public void setOrderNo(String orderNo) \{

this.orderNo = orderNo;

public float getMoney() \{

return money;

public void setMoney(float money) \{

this.money = money;

5、配置文件

这个实例中有三个重要的配置文件，它们分别是：applicationContext.xml ， Configuration.xml 以及 UserMaper.xml。

applicationContext.xml配置文件里最主要的配置：

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"

xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"

xmlns:p="http://www.springframework.org/schema/p"

xsi:schemaLocation="

http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd

http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd

http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd

http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.0.xsd

http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd"

default-autowire="byName" default-lazy-init="false">

destroy-method="close" p:driverClassName="com.mysql.jdbc.Driver"

p:url="jdbc:mysql://127.0.0.1:3306/yiibai?characterEncoding=utf8"

p:username="root" p:password="" p:maxActive="10" p:maxIdle="10">

class="org.springframework.jdbc.datasource.DataSourceTransactionManager">

配置文件Configuration.xml 的内容如下：

/p>

"http://mybatis.org/dtd/mybatis-3-config.dtd">

UserMaper.xml用于定义查询和数据对象映射，其内容如下：

/p>

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

SELECT u.\*,o.\* FROM \`user\` u, \`order\` o

WHERE u.id=o.user\_id AND u.id=\#\{id\}

SELECT \*

FROM user

WHERE id=\#\{id\}

6、测试执行，输出结果

我们创建一个控制器类在包 com.yiibai.controller 下，类的名称为：UserController.java，这里新增了一个方法：pageList， 对应请求URL是 /orderpages，其代码如下：

package com.yiibai.controller;

import java.util.List;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

import com.yiibai.maper.UserMaper;

import com.yiibai.pojo.Order;

import com.yiibai.util.Page;

// http://localhost:8080/mybatis08-paging/user/orders

@Controller

@RequestMapping("/user")

public class UserController \{

@Autowired

UserMaper userMaper;

/\*\*

\* 某一个用户下的所有订单

\* @param request

\* @param response

\* @return

\*/

@RequestMapping("/orders")

public ModelAndView listall(HttpServletRequest request,

HttpServletResponse response) \{

List orders = userMaper.getUserOrders(1);

System.out.println("orders");

ModelAndView mav = new ModelAndView("user\_orders");

mav.addObject("orders", orders);

return mav;

/\*\*

\* 订单分页

\* @param request

\* @param response

\* @return

\*/

@RequestMapping("/orderpages")

public ModelAndView pageList(HttpServletRequest request,

HttpServletResponse response) \{

int currentPage = request.getParameter("page") == null ? 1 : Integer

.parseInt(request.getParameter("page"));

int pageSize = 3;

if (currentPage <= 0) \{

currentPage = 1;

int currentResult = (currentPage - 1) \* pageSize;

System.out.println(request.getRequestURI());

System.out.println(request.getQueryString());

Page page = new Page();

page.setShowCount(pageSize);

page.setCurrentResult(currentResult);

List orders = userMaper.getOrderListPage(page, 1);

System.out.println("Current page =>" + page);

int totalCount = page.getTotalResult();

int lastPage = 0;

if (totalCount % pageSize == 0) \{

lastPage = totalCount % pageSize;

\} else \{

lastPage = 1 + totalCount / pageSize;

if (currentPage >= lastPage) \{

currentPage = lastPage;

String pageStr = "";

pageStr = String.format(

.getRequestURI()

\+ "?page=" + (currentPage - 1), request.getRequestURI()

\+ "?page=" + (currentPage + 1));

// 制定视图，也就是list.jsp

ModelAndView mav = new ModelAndView("pagelist");

mav.addObject("orders", orders);

mav.addObject("pagelist", pageStr);

return mav;

注意，在这个分页工程中，在 com.yiibai.util 包下新增了几个类，它们分别是：PagePlugin.java，Page.java, PageHelper.java，其中 PagePlugin 是针对 MyBatis 分页的插件。由于代码太多，这里列出 PagePlugin.java 的代码，其它两个类的代码有兴趣的读者可以在下载代码后阅读取研究。PagePlugin.java 的代码如下所示：

package com.yiibai.util;

import java.lang.reflect.Field;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.List;

import java.util.Map;

import java.util.Properties;

import javax.xml.bind.PropertyException;

import org.apache.ibatis.executor.ErrorContext;

import org.apache.ibatis.executor.Executor;

import org.apache.ibatis.executor.ExecutorException;

import org.apache.ibatis.executor.statement.BaseStatementHandler;

import org.apache.ibatis.executor.statement.RoutingStatementHandler;

import org.apache.ibatis.executor.statement.StatementHandler;

import org.apache.ibatis.mapping.BoundSql;

import org.apache.ibatis.mapping.MappedStatement;

import org.apache.ibatis.mapping.ParameterMapping;

import org.apache.ibatis.mapping.ParameterMode;

import org.apache.ibatis.plugin.Interceptor;

import org.apache.ibatis.plugin.Intercepts;

import org.apache.ibatis.plugin.Invocation;

import org.apache.ibatis.plugin.Plugin;

import org.apache.ibatis.plugin.Signature;

import org.apache.ibatis.reflection.MetaObject;

import org.apache.ibatis.reflection.property.PropertyTokenizer;

import org.apache.ibatis.scripting.xmltags.ForEachSqlNode;

import org.apache.ibatis.session.Configuration;

import org.apache.ibatis.session.ResultHandler;

import org.apache.ibatis.session.RowBounds;

import org.apache.ibatis.type.TypeHandler;

import org.apache.ibatis.type.TypeHandlerRegistry;

@Intercepts( \{ @Signature(type = StatementHandler.class, method = "prepare", args = \{ Connection.class \}) \})

public class PagePlugin implements Interceptor \{

private static String dialect = "";

private static String pageSqlId = "";

@SuppressWarnings("unchecked")

public Object intercept(Invocation ivk) throws Throwable \{

if (ivk.getTarget() instanceof RoutingStatementHandler) \{

RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk

.getTarget();

BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper

.getValueByFieldName(statementHandler, "delegate");

MappedStatement mappedStatement = (MappedStatement) ReflectHelper

.getValueByFieldName(delegate, "mappedStatement");

if (mappedStatement.getId().matches(pageSqlId)) \{

BoundSql boundSql = delegate.getBoundSql();

Object parameterObject = boundSql.getParameterObject();

if (parameterObject == null) \{

throw new NullYiibaierException("parameterObject error");

\} else \{

Connection connection = (Connection) ivk.getArgs()\[0\];

String sql = boundSql.getSql();

String countSql = "select count(0) from (" + sql

\+ ") myCount";

System.out.println("总数sql 语句:" + countSql);

PreparedStatement countStmt = connection

.prepareStatement(countSql);

BoundSql countBS = new BoundSql(mappedStatement

.getConfiguration(), countSql, boundSql

.getParameterMappings(), parameterObject);

setParameters(countStmt, mappedStatement, countBS,

parameterObject);

ResultSet rs = countStmt.executeQuery();

int count = 0;

if (rs.next()) \{

count = rs.getInt(1);

rs.close();

countStmt.close();

Page page = null;

if (parameterObject instanceof Page) \{

page = (Page) parameterObject;

page.setTotalResult(count);

\} else if (parameterObject instanceof Map) \{

Map map = (Map) parameterObject;

page = (Page) map.get("page");

if (page == null)

page = new Page();

page.setTotalResult(count);

\} else \{

Field pageField = ReflectHelper.getFieldByFieldName(

parameterObject, "page");

if (pageField != null) \{

page = (Page) ReflectHelper.getValueByFieldName(

parameterObject, "page");

if (page == null)

page = new Page();

page.setTotalResult(count);

ReflectHelper.setValueByFieldName(parameterObject,

"page", page);

\} else \{

throw new NoSuchFieldException(parameterObject

.getClass().getName());

String pageSql = generatePageSql(sql, page);

System.out.println("page sql:" + pageSql);

ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql);

return ivk.proceed();

private void setParameters(PreparedStatement ps,

MappedStatement mappedStatement, BoundSql boundSql,

Object parameterObject) throws SQLException \{

ErrorContext.instance().activity("setting parameters").object(

mappedStatement.getParameterMap().getId());

List parameterMappings = boundSql

.getParameterMappings();

if (parameterMappings != null) \{

Configuration configuration = mappedStatement.getConfiguration();

TypeHandlerRegistry typeHandlerRegistry = configuration

.getTypeHandlerRegistry();

MetaObject metaObject = parameterObject == null ? null

: configuration.newMetaObject(parameterObject);

for (int i = 0; i < parameterMappings.size(); i++) \{

ParameterMapping parameterMapping = parameterMappings.get(i);

if (parameterMapping.getMode() != ParameterMode.OUT) \{

Object value;

String propertyName = parameterMapping.getProperty();

PropertyTokenizer prop = new PropertyTokenizer(propertyName);

if (parameterObject == null) \{

value = null;

\} else if (typeHandlerRegistry

.hasTypeHandler(parameterObject.getClass())) \{

value = parameterObject;

\} else if (boundSql.hasAdditionalParameter(propertyName)) \{

value = boundSql.getAdditionalParameter(propertyName);

\} else if (propertyName

.startsWith(ForEachSqlNode.ITEM\_PREFIX)

&& boundSql.hasAdditionalParameter(prop.getName())) \{

value = boundSql.getAdditionalParameter(prop.getName());

if (value != null) \{

value = configuration.newMetaObject(value)

.getValue(

propertyName.substring(prop

.getName().length()));

\} else \{

value = metaObject == null ? null : metaObject

.getValue(propertyName);

TypeHandler typeHandler = parameterMapping.getTypeHandler();

if (typeHandler == null) \{

throw new ExecutorException(

"There was no TypeHandler found for parameter "

\+ propertyName + " of statement "

\+ mappedStatement.getId());

typeHandler.setParameter(ps, i + 1, value, parameterMapping

.getJdbcType());

private String generatePageSql(String sql, Page page) \{

if (page != null && (dialect != null || !dialect.equals(""))) \{

StringBuffer pageSql = new StringBuffer();

if ("mysql".equals(dialect)) \{

pageSql.append(sql);

pageSql.append(" limit " + page.getCurrentResult() + ","

\+ page.getShowCount());

\} else if ("oracle".equals(dialect)) \{

pageSql

.append("select \* from (select tmp\_tb.\*,ROWNUM row\_id from (");

pageSql.append(sql);

pageSql.append(") tmp\_tb where ROWNUM<=");

pageSql.append(page.getCurrentResult() + page.getShowCount());

pageSql.append(") where row\_id>");

pageSql.append(page.getCurrentResult());

return pageSql.toString();

\} else \{

return sql;

public Object plugin(Object arg0) \{

// TODO Auto-generated method stub

return Plugin.wrap(arg0, this);

public void setProperties(Properties p) \{

dialect = p.getProperty("dialect");

if (dialect == null || dialect.equals("")) \{

try \{

throw new PropertyException("dialect property is not found!");

\} catch (PropertyException e) \{

// TODO Auto-generated catch block

e.printStackTrace();

pageSqlId = p.getProperty("pageSqlId");

if (dialect == null || dialect.equals("")) \{

try \{

throw new PropertyException("pageSqlId property is not found!");

\} catch (PropertyException e) \{

// TODO Auto-generated catch block

e.printStackTrace();

接下来部署 mybatis08-paging 这个工程，启动 tomcat ，打开浏览器输入网址：http://localhost:8080/mybatis08-paging/user/orderpages，显示结果如下：

![037475a5cdec3abd152c11ecca27ed02.png][]

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[08d8ce07b9b1cee43923479a5c108310.png]: https://img-blog.csdnimg.cn/img_convert/08d8ce07b9b1cee43923479a5c108310.png
[037475a5cdec3abd152c11ecca27ed02.png]: https://img-blog.csdnimg.cn/img_convert/037475a5cdec3abd152c11ecca27ed02.png