mybatis分頁實現(非外掛方式)
阿新 • • 發佈：2019-01-28
前面一篇文章介紹了通過攔截器發方式實現mybatis分頁（應該是比較常用的一種方式，網上搜索結果較多），這裡介紹另一種方式：通過程式碼封裝，不改變mybatis框架的任何東西（個人推薦使用該方式），這個程式碼是我老大寫的，個人覺得很好，原理也很簡單，修改也很容易，所以貼出來，供大家參考。
package com.dnkx.base.service; import com.dnkx.base.persistance.BaseMapper; import com.dnkx.base.utils.PaginationSupport; import java.io.Serializable; import java.util.Date; import java.util.List; import java.util.Map; /** * Created by baowp on 2015/8/18. */ public interface BaseService<T extends BaseMapper<E>,E extends Serializable> { E get(Long id); int save(E e); int update(E e); int delete(Long id); /** * 按條件查詢列表 * @param params * @return */ List<E> list(Map params); /** * 按條件查詢記錄數 * @param params * @return */ int count(Map params); /** * 按條件分佈查詢列表 * @param params * @return */ PaginationSupport<E> pageList(Map params); /** * 按條件分佈查詢列表 * @param params * @return */ PaginationSupport<E> pageList(E params); }
上面這個是基礎的service類，需要分頁的業務service都繼承於這個基礎的service
下面的實現類和Mapper類同理：
service實現類，裡面包含了分頁的實現，原理很簡單的
package com.dnkx.base.service.impl; import com.dnkx.base.persistance.BaseMapper; import com.dnkx.base.service.BaseService; import com.dnkx.base.utils.PaginationSupport; import com.dnkx.common.utils.BeanUtil; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import java.io.Serializable; import java.util.Date; import java.util.List; import java.util.Map; /** * Created by baowp on 2015/8/18. */ public class BaseServiceImpl<T extends BaseMapper<E>, E extends Serializable> implements BaseService<T, E> { protected final Logger logger = LoggerFactory.getLogger(getClass()); @Autowired protected T mapper; @Override public E get(Long id) { return mapper.get(id); } @Override public int save(E e) { return mapper.save(e); } @Override public int update(E e) { return mapper.update(e); } @Override public int delete(Long id) { return mapper.delete(id); } @Override public List<E> list(Map params) { return mapper.list(params); } @Override public int count(Map params) { return mapper.count(params); } @Override public PaginationSupport<E> pageList(Map params) { if (params.get("pageSize") == null || params.get("pageNo") == null) { throw new RuntimeException("You must specify pageSize and pageNo in the params when executing pageList method"); } int pageSize = (Integer) params.get("pageSize"); int pageNo = (Integer) params.get("pageNo"); if (pageNo < 1) pageNo = 1; //for oracle int startRow = (pageNo - 1) * pageSize; int endRow = startRow + pageSize; params.put("startRow", startRow); params.put("endRow", endRow); //for mysql params.put("startIndex", startRow); List<E> list = mapper.pageList(params); int total = count(params); if (logger.isInfoEnabled()) { logger.info("Get totalCount is {} when executing pageList,pageSize is {},pageNo is {}", total, pageSize, pageNo); } return new PaginationSupport<>(list, total, pageSize, startRow); } @Override public PaginationSupport<E> pageList(E params) { return pageList(BeanUtil.bean2map(params)); } }
Mapper基礎類（更習慣叫DAO）：
package com.dnkx.base.persistance; import java.io.Serializable; import java.util.Date; import java.util.List; import java.util.Map; /** * Created by baowp on 2015/8/18. */ public interface BaseMapper<E extends Serializable> { E get(Long id); int save(E e); int update(E e); int delete(Long id); /** * 按條件查詢列表 * @param params * @return */ List<E> list(Map params); /** * 按條件查詢記錄數 * @param params * @return */ int count(Map params); /** * 按條件分佈查詢列表 * @param params * @return */ List<E> pageList(Map params); }
最後是一個分頁實體物件
package com.dnkx.base.utils;
import java.io.Serializable;
import java.util.Iterator;
import java.util.List;
public class PaginationSupport<E> implements Iterable<E>, Serializable {
public final static int PAGESIZE = 2;
private int pageSize = PAGESIZE;
private int totalCount;
private int currentPage;
private int nextPage;
private int previousPage;
private int startIndex;
private int[] indexes = new int[0];
private int nextIndex;
private int previousIndex;
private int pageCount;
private List<E> items;
private int lastIndex;
public PaginationSupport(){}
public PaginationSupport(int pageSize, int startIndex) {
setPageSize(pageSize);
startIndex(startIndex);
}
public PaginationSupport(List<E> items, int totalCount) {
setPageSize(PAGESIZE);
totalCount(totalCount);
setItems(items);
startIndex(0);
}
public PaginationSupport(List<E> items, int totalCount, int startIndex) {
setPageSize(PAGESIZE);
totalCount(totalCount);
setItems(items);
startIndex(startIndex);
}
public PaginationSupport(List<E> items, int totalCount, int pageSize,
int startIndex) {
setPageSize(pageSize);
totalCount(totalCount);
setItems(items);
startIndex(startIndex);
}
public void totalCount(int totalCount) {
if (totalCount > 0) {
this.totalCount = totalCount;
int count = totalCount / pageSize;
if (totalCount % pageSize > 0)
count++;
indexes = new int[count];
for (int i = 0; i < count; i++) {
indexes[i] = pageSize * i;
}
} else {
this.totalCount = 0;
}
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
}
public int getTotalCount() {
return totalCount;
}
public void setIndexes(int[] indexes) {
this.indexes = indexes;
}
public int[] getIndexes() {
return indexes;
}
public void startIndex(int startIndex) {
if (totalCount <= 0)
this.startIndex = 0;
else if (startIndex >= totalCount)
this.startIndex = indexes[indexes.length - 1];
else if (startIndex < 0)
this.startIndex = 0;
else {
this.startIndex = indexes[startIndex / pageSize];
}
{
pageCount = indexes.length;
currentPage = startIndex / pageSize + 1;
previousPage = currentPage > 1 ? currentPage - 1 : currentPage;
nextPage = currentPage < pageCount ? currentPage + 1 : currentPage;
nextIndex = startIndex + pageSize;
nextIndex = nextIndex >= totalCount ? startIndex : nextIndex;
previousIndex = startIndex - pageSize;
previousIndex = previousIndex < 0 ? 0 : previousIndex;
lastIndex = indexes.length == 0 ? 0 : indexes[indexes.length - 1];
}
}
public void setStartIndex(int startIndex) {
this.startIndex = startIndex;
}
public int getStartIndex() {
return startIndex;
}
public void setNextIndex(int nextIndex) {
this.nextIndex = nextIndex;
}
public int getNextIndex() {
return nextIndex;
}
public void setPreviousIndex(int previousIndex) {
this.previousIndex = previousIndex;
}
public int getPreviousIndex() {
return previousIndex;
}
public void setPageCount(int pageCount) {
this.pageCount = pageCount;
}
public int getPageCount() {
return pageCount;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public void setLastIndex(int lastIndex) {
this.lastIndex = lastIndex;
}
public int getLastIndex() {
return lastIndex;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public List<E> getItems() {
return items;
}
public void setItems(List<E> items) {
this.items = items;
}
public int getNextPage() {
return nextPage;
}
public void setNextPage(int nextPage) {
this.nextPage = nextPage;
}
public int getPreviousPage() {
return previousPage;
}
public void setPreviousPage(int previousPage) {
this.previousPage = previousPage;
}
public Iterator<E> iterator() {
return items.iterator();
}
public int size() {
return items.size();
}
}下面給一個使用例項：
service類
public interface CategoryService extends BaseService<CategoryMapper,CategoryEntity>{
}setviceImpl類
@Service("categoryService")
public class CategoryServiceImpl extends BaseServiceImpl<CategoryMapper,CategoryEntity> implements CategoryService{
}Mapper類
public interface CategoryMapper extends BaseMapper<CategoryEntity>{}Controller類
@Controller
public class CategoryController {
@Resource
private CategoryService categoryService;
@Resource
private HttpServletRequest request;
private final Logger logger= LoggerFactory.getLogger(getClass());
@ResponseBody
@RequestMapping("/category/list")
public String list(){
Map map=new HashMap();
map.put("pageSize",20);
map.put("pageNo",1);
PaginationSupport<CategoryEntity> entity=categoryService.pageList(map);
logger.info("====>{},{}",entity.getItems().size(),entity.getPageCount());
return "";
}
}mapper.xml
<select id="count" parameterType="java.util.Map" resultType="int">
select count(id) from com_category
<include refid="queryConditions"/>
</select>
<select id="pageList" resultMap="BaseResultMap" parameterType="java.util.Map" >
select
<include refid="Base_Column_List" />
from com_category
<include refid="queryConditions" />
limit #{startIndex},#{pageSize}
</select>表達能力欠佳，所以程式碼算是給的比較全了，裡面的原理都很簡單，瞭解OOP的應該都能看明白！！！