mybatis-plus分页查询的实现示例_Java

按照官方文档进行的配置：

引入依赖：

<!-- 引入mybatisplus -->
  　　<dependency>
   <groupid>com.baomidou</groupid>
   <artifactid>mybatis-plus-boot-starter</artifactid>
   <version>3.2.0</version>
  </dependency>
  <!-- 引入mysql驱动包 -->
  <dependency>
   <groupid>mysql</groupid>
   <artifactid>mysql-connector-java</artifactid>
   <version>5.1.27</version>
  </dependency>
  <!-- 引入druid依赖，阿里巴巴所提供的数据源 -->
  <dependency>
   <groupid>com.alibaba</groupid>
   <artifactid>druid</artifactid>
   <version>1.0.29</version>
　　　　</dependency>

在application.yml配置

spring:
 datasource:
 type: com.alibaba.druid.pool.druiddatasource
 driver-class-name: com.mysql.jdbc.driver
 url: jdbc:mysql://127.0.0.1:3306/test?useunicode=true&characterencoding=utf-8
 username: root
 password: 123456

在启动类上面添加@mapperscan注解，扫描mapper包

@springbootapplication
@mapperscan("com.qiao.demo02.mapper")
public class springbootdemo02application {

 public static void main(string[] args) {
  springapplication.run(springbootdemo02application.class, args);
 }

}

新建user和usermapper

user类

@data
public class user {
 @tableid
 private integer userid;
 private string username;
 private integer userage;
 private string useremail;
}

usermapper接口

 public interface usermapper extends basemapper<user> {
 
 }

最重要的是继承basemapper<e>接口：里面声明了很强大的crud方法

public interface basemapper<t> extends mapper<t> {
 int insert(t entity);

 int deletebyid(serializable id);

 int deletebymap(@param("cm") map<string, object> columnmap);

 int delete(@param("ew") wrapper<t> wrapper);

 int deletebatchids(@param("coll") collection<? extends serializable> idlist);

 int updatebyid(@param("et") t entity);

 int update(@param("et") t entity, @param("ew") wrapper<t> updatewrapper);

 t selectbyid(serializable id);

 list<t> selectbatchids(@param("coll") collection<? extends serializable> idlist);

 list<t> selectbymap(@param("cm") map<string, object> columnmap);

 t selectone(@param("ew") wrapper<t> querywrapper);

 integer selectcount(@param("ew") wrapper<t> querywrapper);

 list<t> selectlist(@param("ew") wrapper<t> querywrapper);

 list<map<string, object>> selectmaps(@param("ew") wrapper<t> querywrapper);

 list<object> selectobjs(@param("ew") wrapper<t> querywrapper);

 ipage<t> selectpage(ipage<t> page, @param("ew") wrapper<t> querywrapper);

 ipage<map<string, object>> selectmapspage(ipage<t> page, @param("ew") wrapper<t> querywrapper);
}

分页查询

这点官方文档讲的也很详细：

新建一个config包，在里面建一个mybatisplus配置类返回一个分页拦截器

package com.qiao.demo02.config;

@configuration
@conditionalonclass(value = {paginationinterceptor.class})
public class mybatisplusconfig {
 @bean
 public paginationinterceptor paginationinterceptor() {
  paginationinterceptor paginationinterceptor = new paginationinterceptor();
  return paginationinterceptor;
 }
}

这样就能使用mybatis的分页功能了

junit测试

@resource
 private usermapper usermapper;
 @test
 public void queryuserforpage(){
  ipage<user> userpage = new page<>(2, 2);//参数一是当前页，参数二是每页个数
  userpage = usermapper.selectpage(userpage, null);
  list<user> list = userpage.getrecords();
  for(user user : list){
   system.out.println(user);
  }
 }

controller返回json串

先定义一个包装类uservo，用来保存分页所需要的数据

package com.qiao.demo02.vo;

@data
public class uservo {
 private integer current;
 private integer size;
 private long total;
 private list<user> userlist;
}

然后在控制器编写代码，这里省略了service层，实际开发业务代码写在service层，controller只负责：接受参数、调用service层方法处理业务逻辑，返回结果

controller类贴上了@restcontroller注解

 @getmapping("queryuser")
 public uservo querylist(integer current, integer size) {
  /**
   * 这些代码应该写在service层
   */
  uservo uservo = new uservo();
  ipage<user> page = new page<>(current, size);
  usermapper.selectpage(page, null);
  uservo.setcurrent(current);
  uservo.setsize(size);
  uservo.settotal(page.gettotal());
  uservo.setuserlist(page.getrecords());
  return uservo;
 }

附上结果，前端直接处理json数据即可