基于SpringData封装的 list转page工具类

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());
    }