Mybatis-Plus作分页条件查询

目录

1.添加依赖

2.配置分页拦截器

3.条件查询（MVC架构示例）

（2）数据传输对象DTO

（3）Mapper接口

（4）Mapper.xml

（5）Service层

（6）Controller层

（7）sql创建

4.结果示例

（1）以price为3000.0时查出的结果为例

 （2）不添加任何条件时默认全部查询

---

1.添加依赖

        
        
            com.baomidou
            mybatis-plus-boot-starter
            3.4.3.3
        

注意：版本最好是3.4以上的 

2.配置分页拦截器

import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisPlusConfig {

    /**
     * 分页插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();

        // 分页拦截器
        PaginationInnerInterceptor innerInterceptor = new PaginationInnerInterceptor();
        // 设置请求页数大于最大页时的操作：true 调回到首页，false 继续请求，默认为 false
        innerInterceptor.setOverflow(false);
        // 设置单页的限制数量，-1 表示不限制
        innerInterceptor.setMaxLimit(500L);

        interceptor.addInnerInterceptor(innerInterceptor);
        return interceptor;
    }

}

3.条件查询（MVC架构示例）

（1）实体类Product

import com.baomidou.mybatisplus.annotation.TableField;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@AllArgsConstructor
@NoArgsConstructor
public class Product implements Serializable {


    private Integer pid;

    private String pname;

    private Double price;

    @TableField(value = "category_id")
    private String categoryId;

    private static final long serialVersionUID = 1L;

    public Integer getPid() {
        return pid;
    }

    public void setPid(Integer pid) {
        this.pid = pid;
    }

    public String getPname() {
        return pname;
    }

    public void setPname(String pname) {
        this.pname = pname == null ? null : pname.trim();
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    public String getCategoryId() {
        return categoryId;
    }

    public void setCategoryId(String categoryId) {
        this.categoryId = categoryId == null ? null : categoryId.trim();
    }
}

（2）数据传输对象DTO

        DTO可以理解成是用来封装条件查询属性的集合

        这里以下面三个属性作为条件进行查询

import lombok.Data;

@Data
public class ProductDTO {

    private Integer pid;

    private String pname;

    private Double price;

}

（3）Mapper接口

注意这里一定要继承Mybatis-plus提供的BaseMapper接口

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.zhan.springboot.springbootmybatis.pojo.DTO.ProductDTO;
import com.zhan.springboot.springbootmybatis.pojo.Product;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;


@Mapper
public interface ProductMapper extends BaseMapper {
    IPage selectProduct(IPage page, @Param("productDTO")ProductDTO productDTO);
｝

（4）Mapper.xml

  
      select *
      from springboot.product
      
        pid=#{productDTO.pid}
        And pname=#{productDTO.pname}
        And price=#{productDTO.price}
      
  

这里的条件查询可以自定义，例如增加模糊查询 

（5）Service层

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.zhan.springboot.springbootmybatis.pojo.DTO.ProductDTO;
import com.zhan.springboot.springbootmybatis.pojo.Product;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;

@Mapper
public interface ProductService {

    IPage selectProduct(int pageNum, int pageSize, @Param("productDTO")ProductDTO productDTO);
｝

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.zhan.springboot.springbootmybatis.mapper.ProductMapper;
import com.zhan.springboot.springbootmybatis.pojo.DTO.ProductDTO;
import com.zhan.springboot.springbootmybatis.pojo.Product;
import com.zhan.springboot.springbootmybatis.service.ProductService;
import org.apache.ibatis.annotations.Param;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class ProductServiceImpl implements ProductService {

    @Autowired
    private ProductMapper productMapper;


    @Override
    public IPage selectProduct(int pageNum, int pageSize, @Param("productDTO")ProductDTO productDTO) {
        Page page = new Page<>(pageNum, pageSize);
        // 非空判断
        if (productDTO == null) {
            productDTO = new ProductDTO();
        }
        return productMapper.selectProduct(page,productDTO);
    }
｝

（6）Controller层

import com.zhan.springboot.springbootmybatis.Common.AjaxResult;
import com.zhan.springboot.springbootmybatis.pojo.DTO.ProductDTO;
import com.zhan.springboot.springbootmybatis.pojo.Product;
import com.zhan.springboot.springbootmybatis.service.ProductService;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
@ResponseBody
@RequestMapping("/product")
public class ProductController {
    @Autowired
    private ProductService productService;

    @PostMapping
    public AjaxResult selectProduct(@RequestParam(defaultValue = "1")int pageNum, @RequestParam(defaultValue = "5")int pageSize, @RequestBody(required = false)ProductDTO productDTO){

        return AjaxResult.success(productService.selectProduct(pageNum,pageSize,productDTO));

    }

}

注意这里的AjaxResult是统一封装返回结果集，可以自定义，也可以参考我之前的博客。 

（7）sql创建

create table product
(
    pid         int auto_increment
        primary key,
    pname       varchar(20) not null,
    price       double      null,
    category_id varchar(20) null
);

这里自定义添加数据

4.结果示例

（1）以price为3000.0时查出的结果为例

 （2）不添加任何条件时默认全部查询