EasyCode实现完整CRUD + 分页封装

文章目录

- 1.创建一个表sys-user
- 2.EasyCode 模板配置
- - - 1.entity.java.vm
    - 2.dao.java.vm
    - 3.mapper.xml.vm
    - 4.service.java.vm
    - 5.serviceImpl.java.vm
    - 6.controller.java.vm
    - 7.PageInfo.java.vm
    - 8.PageResult.java.vm
    - 9.SunPageHelper.java.vm
- 3.EasyCode生成CRUD
- - - 1.右键表，选择Generate Code
    - 2.配置
    - 3.查看生成代码
    - 4.对代码做一处调整
    - - Controller的 Result替换为自己封装的响应
- 4.分页封装的代码
- - - 1.PageInfo.java
    - 2.PageResult.java
    - 3.SunPageHelper.java
    - 4.使用方式
    - - 1.DTO实体类继承PageInfo
      - 2.具体使用
      - 1.传入pageNo和pageSize
        2.传入计算数量的逻辑
        3.传入分页查询的逻辑

1.创建一个表sys-user

-- auto-generated definition
create table sys_user
(
    id          bigint auto_increment
        primary key,
    name        varchar(16) null,
    age         int         null,
    create_by   varchar(64) null,
    create_time timestamp   null,
    update_by   varchar(64) null,
    update_time timestamp   null,
    delete_flag tinyint     null,
    version     int         null
)
    charset = utf8mb4;

2.EasyCode 模板配置

1.entity.java.vm

##引入宏定义
$!{define.vm}

##设置保存名称与保存位置
$!callback.setFileName($tool.append($!{tableInfo.name}, ".java"))
$!callback.setSavePath($tool.append($tableInfo.savePath, "/entity"))

##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end

#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.#{end}entity;

import $!{tableInfo.savePackageName}.entity.page.PageInfo;
import lombok.Data;
import lombok.experimental.Accessors;
import java.io.Serializable;
import java.util.Date;

/**
 * $!{tableInfo.comment}($!{tableInfo.name})实体类
 *
 * @author $!author
 * @since $!time.currTime()
 */
@Data
@Accessors(chain = true) // 支持链式调用
public class $!{tableInfo.name} extends PageInfo implements Serializable {

    private static final long serialVersionUID = 1L;

#foreach($column in $tableInfo.fullColumn)
    #if($column.comment)/**
     * $column.comment
     */#end
    private $!{tool.getClsNameByFullName($column.type)} $!{column.name};
    
#end
}

2.dao.java.vm

##定义初始变量
#set($tableName = $tool.append($tableInfo.name, "Mapper"))
##设置回调
$!callback.setFileName($tool.append($tableName, ".java"))
$!callback.setSavePath($tool.append($tableInfo.savePath, "/mapper"))
 
##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end
 
#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.mapper;#end
 
import $!{tableInfo.savePackageName}.entity.$!{tableInfo.name};
import org.apache.ibatis.annotations.Param;
import java.util.List;
 
/**
 * $!{tableInfo.comment}($!{tableInfo.name})表数据库访问层
 *
 * @author $!author
 * @since $!time.currTime()
 */
public interface $!{tableName} {
 
    /**
     * 通过ID查询单条数据
     *
     * @param $!pk.name 主键
     * @return 实例对象
     */
    $!{tableInfo.name} queryById($!pk.shortType $!pk.name);

    /**
     * 分页查询
     *
     * @param po
     * @param offset 偏移量：计算公式 (pageNo - 1) * pageSize
     * @param pageSize 页面大小
     * @return 对象列表
     */
    List<$!{tableInfo.name}> queryPage(@Param("po") $!{tableInfo.name} po, @Param("offset") Integer offset, @Param("pageSize") Integer pageSize);

    /**
     * 根据条件查询记录
     *
     * @param po
     * @return 对象列表
     */
    List<$!{tableInfo.name}> queryAllByLimit(@Param("po") $!{tableInfo.name} po);
 
    /**
     * 统计总行数
     *
     * @param po 查询条件
     * @return 总行数
     */
    Integer count($!{tableInfo.name} po);
 
    /**
     * 新增数据
     *
     * @param po 实例对象(会封装新增的id)
     * @return 影响行数
     */
    int insert($!{tableInfo.name} po);
 
    /**
     * 批量新增数据（MyBatis原生foreach方法）
     *
     * @param entities 实例对象列表(会封装新增的id)
     * @return 影响行数
     */
    int insertBatch(@Param("entities") List<$!{tableInfo.name}> entities);
 
    /**
     * 批量新增或按主键更新数据（MyBatis原生foreach方法）
     *
     * @param entities 实例对象列表
     * @return 影响行数
     * @throws org.springframework.jdbc.BadSqlGrammarException 入参是空List的时候会抛SQL语句错误的异常，请自行校验入参
     */
    int insertOrUpdateBatch(@Param("entities") List<$!{tableInfo.name}> entities);
 
    /**
     * 修改数据
     *
     * @param po 实例对象
     * @return 影响行数
     */
    int update($!{tableInfo.name} po);
 
    /**
     * 通过主键删除数据
     *
     * @param $!pk.name 主键
     * @return 影响行数
     */
    int deleteById($!pk.shortType $!pk.name);
 
}

3.mapper.xml.vm

##引入mybatis支持
$!{mybatisSupport.vm}

##设置保存名称与保存位置
$!callback.setFileName($tool.append($!{tableInfo.name}, "Mapper.xml"))
$!callback.setSavePath($tool.append($modulePath, "/src/main/resources/mapper"))

##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end

<?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="$!{tableInfo.savePackageName}.mapper.$!{tableInfo.name}Mapper">

    <resultMap type="$!{tableInfo.savePackageName}.entity.$!{tableInfo.name}" id="$!{tableInfo.name}Map">
#foreach($column in $tableInfo.fullColumn)
        <result property="$!column.name" column="$!column.obj.name"/>
#end
    </resultMap>

    <!--查询单个-->
    <select id="queryById" resultMap="$!{tableInfo.name}Map">
        select #allSqlColumn() 
        from $!tableInfo.obj.name
        where $!pk.obj.name = #{$!pk.name}
    </select>

    <!--分页查询指定行数据-->
    <select id="queryPage" resultMap="$!{tableInfo.name}Map">
        select #allSqlColumn()
        from $!tableInfo.obj.name
        <where>
#foreach($column in $tableInfo.fullColumn)
            <if test="po.$!column.name != null#if($column.type.equals('java.lang.String')) and po.$!column.name != ''#end">
                and $!column.obj.name = #{po.$!column.name}
            </if>
#end
        </where>
        limit #{offset}, #{pageSize}
    </select>

    <!--根据条件查询记录-->
    <select id="queryAllByLimit" resultMap="$!{tableInfo.name}Map">
        select #allSqlColumn()
        from $!tableInfo.obj.name
        <where>
#foreach($column in $tableInfo.fullColumn)
            <if test="po.$!column.name != null#if($column.type.equals('java.lang.String')) and po.$!column.name != ''#end">
                and $!column.obj.name = #{po.$!column.name}
            </if>
#end
        </where>
    </select>

    <!--统计总行数-->
    <select id="count" resultType="java.lang.Integer">
        select count(1)
        from $!tableInfo.obj.name
        <where>
#foreach($column in $tableInfo.fullColumn)
            <if test="$!column.name != null#if($column.type.equals('java.lang.String')) and $!column.name != ''#end">
                and $!column.obj.name = #{$!column.name}
            </if>
#end
        </where>
    </select>

    <!--新增所有列-->
    <insert id="insert" keyProperty="$!pk.name" useGeneratedKeys="true">
        insert into $!{tableInfo.obj.name}(#foreach($column in $tableInfo.otherColumn)$!column.obj.name#if($foreach.hasNext), #end#end)
        values (#foreach($column in $tableInfo.otherColumn)#{$!{column.name}}#if($foreach.hasNext), #end#end)
    </insert>

    <insert id="insertBatch" keyProperty="$!pk.name" useGeneratedKeys="true">
        insert into $!{tableInfo.obj.name}(#foreach($column in $tableInfo.otherColumn)$!column.obj.name#if($foreach.hasNext), #end#end)
        values
        <foreach collection="entities" item="entity" separator=",">
            <trim prefix="(" suffix=")" suffixOverrides=",">
#foreach($column in $tableInfo.otherColumn)
                <choose>
                    <when test="entity.${column.name} != null">
                        #{entity.$!{column.name}}, 
                    </when>
                    <otherwise>
                        NULL, 
                    </otherwise>
                </choose>
#end
            </trim>
        </foreach>
    </insert>

    <insert id="insertOrUpdateBatch" keyProperty="$!pk.name" useGeneratedKeys="true">
        insert into $!{tableInfo.obj.name}(id, #foreach($column in $tableInfo.otherColumn)$!column.obj.name#if($foreach.hasNext), #end#end)
        values
        <foreach collection="entities" item="entity" separator=",">
            (#{entity.id}, #foreach($column in $tableInfo.otherColumn)#{entity.$!{column.name}}#if($foreach.hasNext), #end#end)
        </foreach>
        on duplicate key update
#foreach($column in $tableInfo.otherColumn)
         $!column.obj.name = values($!column.obj.name)#if($foreach.hasNext),
        #end#end
    </insert>

    <!--通过主键修改数据-->
    <update id="update">
        update $!{tableInfo.obj.name}
        <set>
#foreach($column in $tableInfo.otherColumn)
            <if test="$!column.name != null#if($column.type.equals('java.lang.String')) and $!column.name != ''#end">
                $!column.obj.name = #{$!column.name},
            </if>
#end
        </set>
        where $!pk.obj.name = #{$!pk.name}
    </update>

    <!--通过主键删除-->
    <delete id="deleteById">
        delete from $!{tableInfo.obj.name} where $!pk.obj.name = #{$!pk.name}
    </delete>

</mapper>

4.service.java.vm

##定义初始变量
#set($tableName = $tool.append($tableInfo.name, "Service"))
##设置回调
$!callback.setFileName($tool.append($tableName, ".java"))
$!callback.setSavePath($tool.append($tableInfo.savePath, "/service"))

##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end

#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.service;#end

import $!{tableInfo.savePackageName}.entity.$!{tableInfo.name};
import $!{tableInfo.savePackageName}.entity.page.PageResult;
import java.util.List;

/**
 * $!{tableInfo.comment}($!{tableInfo.name})表服务接口
 *
 * @author $!author
 * @since $!time.currTime()
 */
public interface $!{tableName} {

    /**
     * 通过ID查询单条数据
     *
     * @param $!pk.name 主键
     * @return 实例对象
     */
    $!{tableInfo.name} queryById($!pk.shortType $!pk.name);

    /**
     * 分页查询
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 筛选条件
     * @return 查询结果
     */
    PageResult<$!{tableInfo.name}> queryByPage($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name}));

    /**
     * 根据条件查询记录
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 筛选条件
     * @return 查询结果
     */
    List<$!{tableInfo.name}> queryAllByLimit($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name}));

    /**
     * 新增数据
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 实例对象
     * @return 实例对象
     */
    $!{tableInfo.name} insert($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name}));

    /**
     * 修改数据
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 实例对象
     * @return 实例对象
     */
    $!{tableInfo.name} update($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name}));

    /**
     * 通过主键删除数据
     *
     * @param $!pk.name 主键
     * @return 是否成功
     */
    boolean deleteById($!pk.shortType $!pk.name);

}

5.serviceImpl.java.vm

##定义初始变量
#set($tableName = $tool.append($tableInfo.name, "ServiceImpl"))
##设置回调
$!callback.setFileName($tool.append($tableName, ".java"))
$!callback.setSavePath($tool.append($tableInfo.savePath, "/service/impl"))

##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end

#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.#{end}service.impl;

import $!{tableInfo.savePackageName}.entity.$!{tableInfo.name};
import $!{tableInfo.savePackageName}.mapper.$!{tableInfo.name}Mapper;
import $!{tableInfo.savePackageName}.service.$!{tableInfo.name}Service;
import $!{tableInfo.savePackageName}.entity.page.PageResult;
import $!{tableInfo.savePackageName}.entity.page.SunPageHelper;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

/**
 * $!{tableInfo.comment}($!{tableInfo.name})表服务实现类
 *
 * @author $!author
 * @since $!time.currTime()
 */
@Service("$!tool.firstLowerCase($!{tableInfo.name})Service")
public class $!{tableName} implements $!{tableInfo.name}Service {

    @Resource
    private $!{tableInfo.name}Mapper $!tool.firstLowerCase($!{tableInfo.name})Mapper;

    /**
     * 通过ID查询单条数据
     *
     * @param $!pk.name 主键
     * @return 实例对象
     */
    @Override
    public $!{tableInfo.name} queryById($!pk.shortType $!pk.name) {
        return this.$!{tool.firstLowerCase($!{tableInfo.name})}Mapper.queryById($!pk.name);
    }

    /**
     * 分页查询
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 筛选条件，需要携带pageNo和pageSize以及查询条件
     * @return 分页结果
     */
    @Override
    public PageResult<$!{tableInfo.name}> queryByPage($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name})) {
        // 使用 SunPageHelper 执行分页操作
        return SunPageHelper.paginate($!{tool.firstLowerCase($!{tableInfo.name})}.getPageNo(), $!{tool.firstLowerCase($!{tableInfo.name})}.getPageSize(),
            () -> $!tool.firstLowerCase($!{tableInfo.name})Mapper.count($!tool.firstLowerCase($!{tableInfo.name})),
            (offset, size) -> $!tool.firstLowerCase($!{tableInfo.name})Mapper.queryPage($!tool.firstLowerCase($!{tableInfo.name}), offset, size)
        );
    }

    /**
     * 根据条件查询记录
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 筛选条件
     * @return 查询结果
     */
    @Override
    public List<$!{tableInfo.name}> queryAllByLimit($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name})) {
        return this.$!{tool.firstLowerCase($!{tableInfo.name})}Mapper.queryAllByLimit($!tool.firstLowerCase($!{tableInfo.name}));
    }

    /**
     * 新增数据
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 实例对象
     * @return 实例对象
     */
    @Override
    public $!{tableInfo.name} insert($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name})) {
        this.$!{tool.firstLowerCase($!{tableInfo.name})}Mapper.insert($!tool.firstLowerCase($!{tableInfo.name}));
        return $!tool.firstLowerCase($!{tableInfo.name});
    }

    /**
     * 修改数据
     *
     * @param $!tool.firstLowerCase($!{tableInfo.name}) 实例对象
     * @return 实例对象
     */
    @Override
    public $!{tableInfo.name} update($!{tableInfo.name} $!tool.firstLowerCase($!{tableInfo.name})) {
        this.$!{tool.firstLowerCase($!{tableInfo.name})}Mapper.update($!tool.firstLowerCase($!{tableInfo.name}));
        return this.queryById($!{tool.firstLowerCase($!{tableInfo.name})}.get$!tool.firstUpperCase($pk.name)());
    }

    /**
     * 通过主键删除数据
     *
     * @param $!pk.name 主键
     * @return 是否成功
     */
    @Override
    public boolean deleteById($!pk.shortType $!pk.name) {
        return this.$!{tool.firstLowerCase($!{tableInfo.name})}Mapper.deleteById($!pk.name) > 0;
    }

}

6.controller.java.vm

##定义初始变量
#set($tableName = $tool.append($tableInfo.name, "Controller"))
##设置回调
$!callback.setFileName($tool.append($tableName, ".java"))
$!callback.setSavePath($tool.append($tableInfo.savePath, "/controller"))
##拿到主键
#if(!$tableInfo.pkColumn.isEmpty())
    #set($pk = $tableInfo.pkColumn.get(0))
#end

#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.controller;#end

import $!{tableInfo.savePackageName}.entity.$!{tableInfo.name};
import $!{tableInfo.savePackageName}.service.$!{tableInfo.name}Service;
import $!{tableInfo.savePackageName}.entity.page.PageResult;
import com.sunxiansheng.response.Result;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import java.util.List;

/**
 * $!{tableInfo.comment}($!{tableInfo.name})表控制层
 *
 * @author $!author
 * @since $!time.currTime()
 */
@RestController
@RequestMapping("/$!tool.firstLowerCase($tableInfo.name)")
public class $!{tableName} {
    /**
     * 服务对象
     */
    @Resource
    private $!{tableInfo.name}Service $!tool.firstLowerCase($tableInfo.name)Service;

    /**
     * 通过主键查询单条数据
     *
     * @param $!pk.name 主键
     * @return 单条数据
     */
    @GetMapping("/{id}")
    public Result<$!{tableInfo.name}> queryById(@PathVariable("$!pk.name") $!pk.shortType $!pk.name) {
        return Result.ok(this.$!tool.firstLowerCase($tableInfo.name)Service.queryById($!pk.name));
    }

    /**
     * 分页查询数据
     *
     * @param $!tool.firstLowerCase($tableInfo.name) 筛选条件
     * @return 查询结果
     */
    @GetMapping("/queryPage")
    public PageResult<$!{tableInfo.name}> queryByPage(@RequestBody $!{tableInfo.name} $!tool.firstLowerCase($tableInfo.name)) {
        return this.$!tool.firstLowerCase($tableInfo.name)Service.queryByPage($!tool.firstLowerCase($tableInfo.name));
    }

    /**
     * 根据条件查询记录
     *
     * @param $!tool.firstLowerCase($tableInfo.name) 筛选条件
     * @return 查询结果
     */
    @GetMapping
    public Result<List<$!{tableInfo.name}>> queryAllByLimit(@RequestBody $!{tableInfo.name} $!tool.firstLowerCase($tableInfo.name)) {
        return Result.ok(this.$!tool.firstLowerCase($tableInfo.name)Service.queryAllByLimit($!tool.firstLowerCase($tableInfo.name)));
    }

    /**
     * 新增数据
     *
     * @param $!tool.firstLowerCase($tableInfo.name) 实体
     * @return 新增结果
     */
    @PostMapping
    public Result<$!{tableInfo.name}> add(@RequestBody $!{tableInfo.name} $!tool.firstLowerCase($tableInfo.name)) {
        return Result.ok(this.$!tool.firstLowerCase($tableInfo.name)Service.insert($!tool.firstLowerCase($tableInfo.name)));
    }

    /**
     * 编辑数据
     *
     * @param $!tool.firstLowerCase($tableInfo.name) 实体
     * @return 编辑结果
     */
    @PutMapping
    public Result<$!{tableInfo.name}> edit(@RequestBody $!{tableInfo.name} $!tool.firstLowerCase($tableInfo.name)) {
        return Result.ok(this.$!tool.firstLowerCase($tableInfo.name)Service.update($!tool.firstLowerCase($tableInfo.name)));
    }

    /**
     * 删除数据
     *
     * @param $!pk.name 主键
     * @return 删除是否成功
     */
    @DeleteMapping
    public Result<Boolean> deleteById(@RequestBody $!pk.shortType $!pk.name) {
        return Result.ok(this.$!tool.firstLowerCase($tableInfo.name)Service.deleteById($!pk.name));
    }

}

7.PageInfo.java.vm

##定义初始变量
#set($className = "PageInfo")
##设置回调
$!callback.setFileName($className + ".java")
$!callback.setSavePath($tool.append($tableInfo.savePath, "/entity/page"))
##包名
#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.entity.page;#end

import java.util.Objects;

/**
 * Description: 分页请求的入参
 * @Author $!author
 * @Create $!time.currTime()
 * @Version 1.1
 */
public class $className {

    private Integer pageNo = 1;
    private Integer pageSize = 20;

    public Integer getPageNo() {
        return (pageNo == null || pageNo < 1) ? 1 : pageNo;
    }

    public Integer getPageSize() {
        return (pageSize == null || pageSize < 1) ? 20 : pageSize;
    }

    public $className setPageNo(Integer pageNo) {
        this.pageNo = pageNo;
        return this;
    }

    public $className setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
        return this;
    }

    @Override
    public int hashCode() {
        return Objects.hash(pageNo, pageSize);
    }

    @Override
    public String toString() {
        return "$className{" +
                "pageNo=" + pageNo +
                ", pageSize=" + pageSize +
                '}';
    }
}

8.PageResult.java.vm

##定义初始变量
#set($className = "PageResult")
##设置回调
$!callback.setFileName($className + ".java")
$!callback.setSavePath($tool.append($tableInfo.savePath, "/entity/page"))
##包名
#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.entity.page;#end

import java.util.Collections;
import java.util.List;

import static java.util.Objects.requireNonNull;

/**
 * Description: 分页返回的实体
 * @Author $!author
 * @Create $!time.currTime()
 * @Version 1.1
 */
public class $className<T> {

    // 当前页码，默认为1
    private Integer pageNo = 1;

    // 每页显示的记录数，默认为20
    private Integer pageSize = 20;

    // 总记录条数
    private Integer total = 0;

    // 总页数
    private Integer totalPages = 0;

    // 当前页的记录列表
    private List<T> result = Collections.emptyList();

    // 表示当前页是从分页查询结果的第几条记录开始，下标从1开始
    private Integer start = 1;

    // 表示当前页是从分页查询结果的第几条记录结束，下标从1开始
    private Integer end = 0;

    // 私有构造函数，使用Builder创建实例
    private $className(Builder<T> builder) {
        this.pageNo = builder.pageNo;
        this.pageSize = builder.pageSize;
        this.total = builder.total;
        this.result = builder.result;
        calculateTotalPages();
        calculateStartAndEnd();
    }

    // Builder 模式实现
    public static class Builder<T> {
        private Integer pageNo = 1;
        private Integer pageSize = 20;
        private Integer total = 0;
        private List<T> result = Collections.emptyList();

        public Builder<T> pageNo(Integer pageNo) {
            this.pageNo = requireNonNull(pageNo, "Page number cannot be null");
            return this;
        }

        public Builder<T> pageSize(Integer pageSize) {
            this.pageSize = requireNonNull(pageSize, "Page size cannot be null");
            return this;
        }

        public Builder<T> total(Integer total) {
            this.total = requireNonNull(total, "Total count cannot be null");
            return this;
        }

        public Builder<T> result(List<T> result) {
            this.result = requireNonNull(result, "Result list cannot be null");
            return this;
        }

        public $className<T> build() {
            return new $className<>(this);
        }
    }

    // 计算总页数
    private void calculateTotalPages() {
        if (this.pageSize > 0) {
            this.totalPages = (this.total / this.pageSize) + (this.total % this.pageSize == 0 ? 0 : 1);
        } else {
            this.totalPages = 0;
        }
    }

    // 计算起始和结束位置
    private void calculateStartAndEnd() {
        if (this.pageSize > 0) {
            this.start = (this.pageNo - 1) * this.pageSize + 1;
            this.end = Math.min(this.pageNo * this.pageSize, this.total);
        } else {
            this.start = 1;
            this.end = this.total;
        }
    }

    // 获取当前页的起始位置
    public Integer getStart() {
        return start;
    }

    // 获取每页记录数
    public Integer getPageSize() {
        return pageSize;
    }

    // 获取当前页码
    public Integer getPageNo() {
        return pageNo;
    }

    // 获取总记录条数
    public Integer getTotal() {
        return total;
    }

    // 获取总页数
    public Integer getTotalPages() {
        return totalPages;
    }

    // 获取当前页的记录列表
    public List<T> getResult() {
        return result;
    }

    // 获取当前页的结束位置
    public Integer getEnd() {
        return end;
    }

    @Override
    public String toString() {
        return "$className{" +
                "pageNo=" + pageNo +
                ", pageSize=" + pageSize +
                ", total=" + total +
                ", totalPages=" + totalPages +
                ", result=" + result +
                ", start=" + start +
                ", end=" + end +
                '}';
    }
}

9.SunPageHelper.java.vm

##定义初始变量
#set($className = "SunPageHelper")
##设置回调
$!callback.setFileName($className + ".java")
$!callback.setSavePath($tool.append($tableInfo.savePath, "/entity/page"))
##包名
#if($tableInfo.savePackageName)package $!{tableInfo.savePackageName}.entity.page;#end

import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Supplier;

/**
 * Description: 分页逻辑封装
 * @Author $!author
 * @Create $!time.currTime()
 * @Version 1.0
 */
public class $className {

    /**
     * 执行分页操作
     * @param pageNo 页码
     * @param pageSize 每页记录数
     * @param totalSupplier 获取总记录条数的逻辑
     * @param recordsSupplier 获取记录列表的逻辑
     * @param <T> 记录的类型
     * @return 分页结果
     */
    public static <T> PageResult<T> paginate(int pageNo, int pageSize,
                                             Supplier<Integer> totalSupplier,
                                             BiFunction<Integer, Integer, List<T>> recordsSupplier) {
        // 计算总记录数
        int total;
        try {
            total = totalSupplier.get();
        } catch (Exception e) {
            throw new RuntimeException("Failed to get total count", e);
        }
        
        // 如果总记录数为0，返回空的 PageResult
        if (total == 0) {
            return new PageResult.Builder<T>()
                    .pageNo(pageNo)
                    .pageSize(pageSize)
                    .total(total)
                    .result(Collections.emptyList()) // 空列表
                    .build();
        }

        // 计算 offset，表示从第几条记录开始查询
        int offset = calculateOffset(pageNo, pageSize);

        // 获取当前页的记录列表
        List<T> records;
        try {
            records = recordsSupplier.apply(offset, pageSize);
        } catch (Exception e) {
            throw new RuntimeException("Failed to get records", e);
        }

        // 使用 Builder 模式创建 PageResult 对象并返回
        return new PageResult.Builder<T>()
                .pageNo(pageNo)
                .pageSize(pageSize)
                .total(total)
                .result(records)
                .build();
    }

    /**
     * 计算分页的 offset
     * @param pageNo 页码
     * @param pageSize 每页记录数
     * @return offset
     */
    public static int calculateOffset(int pageNo, int pageSize) {
        // offset 计算公式：(当前页码 - 1) * 每页记录数
        return (pageNo - 1) * pageSize;
    }
}

3.EasyCode生成CRUD

1.右键表，选择Generate Code

CleanShot 2024-07-12 at 16.01.05@2x

2.配置

CleanShot 2024-07-16 at 14.13.08@2x

3.查看生成代码

CleanShot 2024-07-16 at 14.23.01@2x

4.对代码做一处调整

Controller的 Result替换为自己封装的响应

CleanShot 2024-07-16 at 14.16.45@2x

4.分页封装的代码

1.PageInfo.java

package com.sunxiansheng.user.entity.page;
import java.util.Objects;

/**
 * Description: 分页请求的入参
 * @Author sun
 * @Create 2024-07-16 14:14:55
 * @Version 1.1
 */
public class PageInfo {

    private Integer pageNo = 1;
    private Integer pageSize = 20;

    public Integer getPageNo() {
        return (pageNo == null || pageNo < 1) ? 1 : pageNo;
    }

    public Integer getPageSize() {
        return (pageSize == null || pageSize < 1) ? 20 : pageSize;
    }

    public PageInfo setPageNo(Integer pageNo) {
        this.pageNo = pageNo;
        return this;
    }

    public PageInfo setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
        return this;
    }

    @Override
    public int hashCode() {
        return Objects.hash(pageNo, pageSize);
    }

    @Override
    public String toString() {
        return "PageInfo{" +
                "pageNo=" + pageNo +
                ", pageSize=" + pageSize +
                '}';
    }
}

2.PageResult.java

package com.sunxiansheng.user.entity.page;
import java.util.Collections;
import java.util.List;

import static java.util.Objects.requireNonNull;

/**
 * Description: 分页返回的实体
 * @Author sun
 * @Create 2024-07-16 14:14:55
 * @Version 1.1
 */
public class PageResult<T> {

    // 当前页码，默认为1
    private Integer pageNo = 1;

    // 每页显示的记录数，默认为20
    private Integer pageSize = 20;

    // 总记录条数
    private Integer total = 0;

    // 总页数
    private Integer totalPages = 0;

    // 当前页的记录列表
    private List<T> result = Collections.emptyList();

    // 表示当前页是从分页查询结果的第几条记录开始，下标从1开始
    private Integer start = 1;

    // 表示当前页是从分页查询结果的第几条记录结束，下标从1开始
    private Integer end = 0;

    // 私有构造函数，使用Builder创建实例
    private PageResult(Builder<T> builder) {
        this.pageNo = builder.pageNo;
        this.pageSize = builder.pageSize;
        this.total = builder.total;
        this.result = builder.result;
        calculateTotalPages();
        calculateStartAndEnd();
    }

    // Builder 模式实现
    public static class Builder<T> {
        private Integer pageNo = 1;
        private Integer pageSize = 20;
        private Integer total = 0;
        private List<T> result = Collections.emptyList();

        public Builder<T> pageNo(Integer pageNo) {
            this.pageNo = requireNonNull(pageNo, "Page number cannot be null");
            return this;
        }

        public Builder<T> pageSize(Integer pageSize) {
            this.pageSize = requireNonNull(pageSize, "Page size cannot be null");
            return this;
        }

        public Builder<T> total(Integer total) {
            this.total = requireNonNull(total, "Total count cannot be null");
            return this;
        }

        public Builder<T> result(List<T> result) {
            this.result = requireNonNull(result, "Result list cannot be null");
            return this;
        }

        public PageResult<T> build() {
            return new PageResult<>(this);
        }
    }

    // 计算总页数
    private void calculateTotalPages() {
        if (this.pageSize > 0) {
            this.totalPages = (this.total / this.pageSize) + (this.total % this.pageSize == 0 ? 0 : 1);
        } else {
            this.totalPages = 0;
        }
    }

    // 计算起始和结束位置
    private void calculateStartAndEnd() {
        if (this.pageSize > 0) {
            this.start = (this.pageNo - 1) * this.pageSize + 1;
            this.end = Math.min(this.pageNo * this.pageSize, this.total);
        } else {
            this.start = 1;
            this.end = this.total;
        }
    }

    // 获取当前页的起始位置
    public Integer getStart() {
        return start;
    }

    // 获取每页记录数
    public Integer getPageSize() {
        return pageSize;
    }

    // 获取当前页码
    public Integer getPageNo() {
        return pageNo;
    }

    // 获取总记录条数
    public Integer getTotal() {
        return total;
    }

    // 获取总页数
    public Integer getTotalPages() {
        return totalPages;
    }

    // 获取当前页的记录列表
    public List<T> getResult() {
        return result;
    }

    // 获取当前页的结束位置
    public Integer getEnd() {
        return end;
    }

    @Override
    public String toString() {
        return "PageResult{" +
                "pageNo=" + pageNo +
                ", pageSize=" + pageSize +
                ", total=" + total +
                ", totalPages=" + totalPages +
                ", result=" + result +
                ", start=" + start +
                ", end=" + end +
                '}';
    }
}

3.SunPageHelper.java

package com.sunxiansheng.user.entity.page;

import java.util.Collections;
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Supplier;

/**
 * Description: 分页逻辑封装
 * @Author sun
 * @Create 2024-07-16 14:14:55
 * @Version 1.0
 */
public class SunPageHelper {

    /**
     * 执行分页操作
     * @param pageNo 页码
     * @param pageSize 每页记录数
     * @param totalSupplier 获取总记录条数的逻辑
     * @param recordsSupplier 获取记录列表的逻辑
     * @param <T> 记录的类型
     * @return 分页结果
     */
    public static <T> PageResult<T> paginate(int pageNo, int pageSize,
                                             Supplier<Integer> totalSupplier,
                                             BiFunction<Integer, Integer, List<T>> recordsSupplier) {
        // 计算总记录数
        int total;
        try {
            total = totalSupplier.get();
        } catch (Exception e) {
            throw new RuntimeException("Failed to get total count", e);
        }

        // 如果总记录数为0，返回空的 PageResult
        if (total == 0) {
            return new PageResult.Builder<T>()
                    .pageNo(pageNo)
                    .pageSize(pageSize)
                    .total(total)
                    .result(Collections.emptyList()) // 空列表
                    .build();
        }

        // 计算 offset，表示从第几条记录开始查询
        int offset = calculateOffset(pageNo, pageSize);

        // 获取当前页的记录列表
        List<T> records;
        try {
            records = recordsSupplier.apply(offset, pageSize);
        } catch (Exception e) {
            throw new RuntimeException("Failed to get records", e);
        }

        // 使用 Builder 模式创建 PageResult 对象并返回
        return new PageResult.Builder<T>()
                .pageNo(pageNo)
                .pageSize(pageSize)
                .total(total)
                .result(records)
                .build();
    }

    /**
     * 计算分页的 offset
     * @param pageNo 页码
     * @param pageSize 每页记录数
     * @return offset
     */
    public static int calculateOffset(int pageNo, int pageSize) {
        // offset 计算公式：(当前页码 - 1) * 每页记录数
        return (pageNo - 1) * pageSize;
    }
}

4.使用方式

1.DTO实体类继承PageInfo

2.具体使用

1.传入pageNo和pageSize

2.传入计算数量的逻辑

3.传入分页查询的逻辑

    /**
     * 分页查询
     *
     * @param sysUser 筛选条件，需要携带pageNo和pageSize以及查询条件
     * @return 分页结果
     */
    @Override
    public PageResult<SysUser> queryByPage(SysUser sysUser) {
        // 使用 SunPageHelper 执行分页操作
        return SunPageHelper.paginate(sysUser.getPageNo(), sysUser.getPageSize(),
            // 查询数量
            () -> sysUserMapper.count(sysUser),
            // 
            (offset, size) -> sysUserMapper.queryPage(sysUser, offset, size)
        );
    }