List对象转Page对象参考，一行代码实现

野性酷女 2021-10-14 20:01 1503阅读 0赞

## [上一篇 SpringData中Page对象的架构设计][SpringData_Page] ##

### 写在前面 ###

*   *  \[上一篇 SpringData中Page对象的架构设计\](https://blog.csdn.net/qq\_42105629/article/details/99575507)
     *   *  一、代码示例
         *  二、纠正一下，上文的处理是不正确的，可参考以下
     *  这里，还有List的很多操作

### 一、代码示例 ###

@GetMapping("/listTopage")
        public Page listtoPage(){ 
            List<CustomerDTO> customerDTOS = customerMapper.toCustomerDto(customerService.findAll());
            PageImpl page = new PageImpl(customerDTOS, PageRequest.of(0, 20), customerDTOS.size());
            return page;
        }

可以参考下代码实现（部分）

public PageImpl(List<T> content, Pageable pageable, long total) { 
    
    		super(content, pageable);
    
    		this.total = pageable.toOptional().filter(it -> !content.isEmpty())//
    				.filter(it -> it.getOffset() + it.getPageSize() > total)//
    				.map(it -> it.getOffset() + content.size())//
    				.orElse(total);
    	}

***注意***：：这里的处理，只完成了当前页的数据page封装，并不准确

### 二、纠正一下，上文的处理是不正确的，可参考以下 ###

封装工具类

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());
        }
    }

使用时

@GetMapping("/to-page")
        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());
        }

即可完成正确处理

## 这里，还有List的很多操作 ##

*  [List 除重][List]
 *  [List自定义排序输出][List 1]
 *  [List Bean,和Map互转][List Bean_Map]
 *  [Page对象互转][Page]

[SpringData_Page]: https://blog.csdn.net/qq_42105629/article/details/99575507
[List]: https://blog.csdn.net/qq_42105629/article/details/99583889
[List 1]: https://blog.csdn.net/qq_42105629/article/details/99585036
[List Bean_Map]: https://blog.csdn.net/qq_42105629/article/details/99124260
[Page]: https://blog.csdn.net/qq_42105629/article/details/99591993