springboot 分页实现
一、sql分页
基于sql语句的分页，不需要特殊依赖。
1.1 依赖
因为使用了mybatis、mysql ，所以要添加相关依赖。这里版本没有特别需求，选择你想要的版本即可。
<!--mybatis-->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>${mybatis-version}</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql-version}</version>
</dependency>
本人使用的版本：
<mybatis-version>1.3.1</mybatis-version>
<mysql-version>5.1.32</mysql-version>
1.2 Dao层
在ArticleMapper .java中，分页函数如下：
package com.sqlb.mapper;
import com.sqlb.pojo.Article;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;
import java.util.Map;
@Mapper
public interface ArticleMapper {
/**
*sql 分页
*/
List<Article> list(Map<String, Object> map);
}
对应的ArticleMapper .xml中如下：
<select id="list" resultType="com.sqlb.pojo.Article">
select
<include refid="Base_Column_List"/>
from article
<where>
<if test="id != null and id != ''">and id = #{id}</if>
<if test="author != null and author != ''">and author = #{author}</if>
<if test="createTime != null and createTime != ''">and create_time = #{createTime}</if>
<if test="typeName != null and typeName != ''">and type_name = #{typeName}</if>
<if test="imageUrl != null and imageUrl != ''">and image_url = #{imageUrl}</if>
<if test="content != null and content != ''">and content = #{content}</if>
</where>
<choose>
<when test="createTime != null and createTime.trim() != ''">
order by ${createTime}
</when>
<otherwise>
order by id desc
</otherwise>
</choose>
<if test="offset != null and limit != null">
limit #{offset}, #{limit}
</if>
</select>
1.3 Service层
@Service
public class ArticleServiceImpl implements ArticleService {
@Autowired
private ArticleMapper articleMapper;
@Override
public List<Article> list(Integer pageNum, Integer pageSize) {
return articleMapper.list(PageParam.getParams(pageNum, pageSize));
}
}
1.4 Controller层
@Controller
@RequestMapping("/article")
public class ArticleController {
@Autowired
ArticleService articleService;
@ResponseBody
@RequestMapping("/list")
public List<Article> list(@RequestParam(defaultValue = "1",value = "currentPage") Integer pageNum,
@RequestParam(defaultValue = "10",value = "pageSize") Integer pageSize){
return articleService.list(pageNum,pageSize);
}
}
当然，使用mybatis记得在application.yml中配置一把，以及mysql数据连接池配置。
mybatis:
configuration:
map-underscore-to-camel-case: true
mapper-locations: mybatis/*/*Mapper.xml
type-aliases-package: com.sqlb.pojo
mysql数据连接池配置这里就不用多说了吧。不知道的，就赶紧去学习下基础知识。
Article类和表结构
Article类
import java.util.Date;
public class Article {
private Integer id;
private String author;
private Date createTime;
private String typeName;
private String imageUrl;
private String content;
//此处省去get、set方法
}
表结构
CREATE TABLE `article` (
`id` int(11) NOT NULL AUTO_INCREMENT COMMENT 'id编号',
`content` text NOT NULL COMMENT '文章内容，代码控制不可超过1000字',
`author` varchar(128) DEFAULT NULL COMMENT '作者',
`create_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '创建时间',
`type_name` enum('0','1','2','3','4') NOT NULL DEFAULT '1' COMMENT '文章类型',
`image_url` varchar(255) DEFAULT NULL COMMENT '图片地址',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=21 DEFAULT CHARSET=utf8mb4;
sql分页就是这么多了，运行访问http://localhost:8081/article/list可以得到你想要的数据。
二、插件分页
显然，这种方法是要导入第三方jar包的，具体方法如下。
2.1 插件依赖
<!--分页插件-->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>${pagehelper-version}</version>
</dependency>
这里要说明一下，本人使用的版本是：
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.4</version>
</dependency>
2.2 配置
springboot最大的特色就是只需简单的配置，就可以进行快捷的开发，配置如下：
pagehelper:
helper-dialect: mysql
reasonable: true
support-methods-arguments: true
params: count=countSql
需要特别注意的是pagehelper.reasonable=true时，当页码增加时，如果没有分页数据了，会一直返回最后一页的数据。建议使用pagehelper.reasonable=false
2.3 Dao层
ArticleMapper .java
import com.github.pagehelper.Page;
import com.sqlb.pojo.Article;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;
import java.util.Map;
@Mapper
public interface ArticleMapper {
/**
* 插件 分页 查询表中部分字段
*/
Page<Article> findByPage();
/**
* 插件 分页 查询表中所有字段
*/
Page<Article> findWithBLOBsByPage();
}
ArticleMapper .xml
<select id="findByPage" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from article
</select>
<select id="findWithBLOBsByPage" resultMap="ResultMapWithBLOBs">
select
<include refid="Base_Column_List"/>
,
<include refid="Blob_Column_List"/>
from article
</select>
这里有两个分页，不同点就是findWithBLOBsByPage把所有的字段都查询出来了，而findByPage相比之下少查询了一个字段。这里需要提出的是，本人的使用findByPage查询部分字段时，会报java.lang.NoSuchMethodException错误，具体原因暂时不详，以后明白了再记出来，如果哪个大神明白细节的还望不吝赐教~~~
2.4 Service层
此处才用到PageHelper插件
import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.sqlb.mapper.ArticleMapper;
import com.sqlb.pojo.Article;
import com.sqlb.service.ArticleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class ArticleServiceImpl implements ArticleService {
@Autowired
private ArticleMapper articleMapper;
@Override
public Page<Article> findByPage(Integer pageNum, Integer pageSize) {
//用插件进行分页
PageHelper.startPage(pageNum, pageSize);
return articleMapper.findByPage();
}
@Override
public Page<Article> findWithBLOBsByPage(Integer pageNum, Integer pageSize) {
//用插件进行分页
PageHelper.startPage(pageNum, pageSize);
return articleMapper.findWithBLOBsByPage();
}
}
2.5 Controller层
首先要创建一个返回给前端的pojo对象，新建一个分页数据类PageInfo：
import com.github.pagehelper.Page;
import java.io.Serializable;
import java.util.Collection;
import java.util.List;
/**
* @描叙： 分页 数据结构
*/
public class PageInfo<T> implements Serializable {
private static final long serialVersionUID = 1L;
//当前页
private int pageNum;
//每页的数量
private int pageSize;
//总记录数
private long total;
//总页数
private int pages;
//结果集
private List<T> list;
//是否为第一页
private boolean isFirstPage = false;
//是否为最后一页
private boolean isLastPage = false;
public PageInfo() {
}
/**
* 包装Page对象
*
* @param list
*/
public PageInfo(List<T> list) {
if (list instanceof Page) {
Page page = (Page) list;
this.pageNum = page.getPageNum();
this.pageSize = page.getPageSize();
this.pages = page.getPages();
this.list = page;
this.total = page.getTotal();
} else if (list instanceof Collection) {
this.pageNum = 1;
this.pageSize = list.size();
this.pages = 1;
this.list = list;
this.total = list.size();
}
if (list instanceof Collection) {
//判断页面边界
judgePageBoudary();
}
}
/**
* 判定页面边界
*/
private void judgePageBoudary() {
isFirstPage = pageNum == 1;
isLastPage = pageNum == pages;
}
public int getPageNum() {
return pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public long getTotal() {
return total;
}
public void setTotal(long total) {
this.total = total;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public List<T> getList() {
return list;
}
public void setList(List<T> list) {
this.list = list;
}
public boolean isIsFirstPage() {
return isFirstPage;
}
public void setIsFirstPage(boolean isFirstPage) {
this.isFirstPage = isFirstPage;
}
public boolean isIsLastPage() {
return isLastPage;
}
public void setIsLastPage(boolean isLastPage) {
this.isLastPage = isLastPage;
}
@Override
public String toString() {
final StringBuffer sb = new StringBuffer("PageInfo{");
sb.append("pageNum=").append(pageNum);
sb.append(", pageSize=").append(pageSize);
sb.append(", total=").append(total);
sb.append(", pages=").append(pages);
sb.append(", list=").append(list);
sb.append(", isFirstPage=").append(isFirstPage);
sb.append(", isLastPage=").append(isLastPage);
sb.append(", navigatepageNums=");
sb.append('}');
return sb.toString();
}
}
ArticleController.java中，数据转换如下：
import com.github.pagehelper.Page;
import com.sqlb.pojo.Article;
import com.sqlb.pojo.PageInfo; //刚才新建的分页数据对象
import com.sqlb.service.ArticleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
@RequestMapping("/article")
public class ArticleController {
@Autowired
ArticleService articleService;
@ResponseBody
@RequestMapping("/page")
public PageInfo<Article> findWithBLOBsByPage(@RequestParam(defaultValue = "1",value = "currentPage") Integer pageNum,
@RequestParam(defaultValue = "10",value = "pageSize") Integer pageSize){
Page<Article> articles = articleService.findWithBLOBsByPage(pageNum, pageSize);
// 需要把Page包装成PageInfo对象才能序列化。该插件也默认实现了一个PageInfo
PageInfo<Article> pageInfo = new PageInfo<>(articles);
return pageInfo;
}
}
插件分页就是这么多了，运行访问http://localhost:8081/article/list可以得到你想要的数据。
