基于SpringData封装的 list转page工具类

忘是亡心i 2023-07-13 04:10 4阅读 0赞

### 基于SpringData封装的 list转page工具类 ###

*   *  写在前面
     *  一、实现一
     *  一、实现二

## 写在前面 ##

这里有两个实现

## 一、实现一 ##

package tonels.util;
    
    import org.springframework.data.domain.Page;
    import org.springframework.data.domain.PageImpl;
    import org.springframework.data.domain.Pageable;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public interface PageUtil { 
    
        /** * Create a {@link org.springframework.data.domain.Page} from a {@link java.util.List} of objects * * @param list List数据 * @param pageable 分页参数. * @param <T> 包含数据 * @return page */
        static <T> Page<T> createPageFromList(List<T> list, Pageable pageable) { 
            if (list == null) { 
                throw new IllegalArgumentException("list不能为空");
            }
    
            int startOfPage = pageable.getPageNumber() * pageable.getPageSize();
            if (startOfPage > list.size()) { 
                return new PageImpl<>(new ArrayList<>(), pageable, 0);
            }
    
            int endOfPage = Math.min(startOfPage + pageable.getPageSize(), list.size());
            return new PageImpl<>(list.subList(startOfPage, endOfPage), pageable, list.size());
        }
    }

使用

@GetMapping("/toPage2")
        public ResultBean toPage2( @RequestParam(defaultValue = "1") int page,
                                   @RequestParam(defaultValue = "20") int rows) { 
            Pageable pageable = PageRequest.of(page - 1, rows);
            List<CustomersEntity> all = customerRepo.findAll();
            Page<CustomersEntity> pageFromList = PageUtil.createPageFromList(all, pageable);
    
            return ResultBean.ok(pageFromList.getTotalPages(),pageFromList.getTotalElements(),pageFromList.getContent());
        }

## 一、实现二 ##

package tonels.util;
    
    import org.springframework.data.domain.Page;
    import org.springframework.data.domain.PageImpl;
    import org.springframework.data.domain.Pageable;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class PageUtilClass { 
    
        // todo 这里比较下 当工具类定义为 interface 和 class 的区别
        // interface 更方便解耦，
    
       public static <T> Page<T> createPageFromList(List<T> list, Pageable pageable) { 
            if (list == null) { 
                throw new IllegalArgumentException("To create a Page, the list mustn't be null!");
            }
    
            int startOfPage = pageable.getPageNumber() * pageable.getPageSize();
            if (startOfPage > list.size()) { 
                return new PageImpl<>(new ArrayList<>(), pageable, 0);
            }
    
            int endOfPage = Math.min(startOfPage + pageable.getPageSize(), list.size());
            return new PageImpl<>(list.subList(startOfPage, endOfPage), pageable, list.size());
        }
    }

使用

@GetMapping("/toPage3")
        public ResultBean toPage3( @RequestParam(defaultValue = "1") int page,
                                   @RequestParam(defaultValue = "20") int rows) { 
            Pageable pageable = PageRequest.of(page - 1, rows);
            List<CustomersEntity> all = customerRepo.findAll();
            Page<CustomersEntity> pageFromList = PageUtilClass.createPageFromList(all, pageable);
    
            return ResultBean.ok(pageFromList.getTotalPages(),pageFromList.getTotalElements(),pageFromList.getContent());
        }