jpa的Pageable和PageRequest的源码

本是古典何须时尚 2022-12-02 01:18 185阅读 0赞

### jpa的Pageable和PageRequest的源码 ###

*  常用方法
 *  Pageable
 *  Unpaged
 *  AbstractPageRequest
 *  PageRequest
 *  QPageRequest

# 常用方法 #

Sort sort01 = new Sort(Direction.ASC, "name");
    		Sort sort02 = Sort.by(Direction.ASC, "name");
    		Order idOrder = new Order(Direction.DESC, "id");
    		Order idOrder2 = new Order(Direction.DESC, "name");
    		Sort sort03 = Sort.by(idOrder,idOrder2);
    		Sort sort04 = Sort.by(Direction.ASC, "id", "name");
    		Sort sort05 = Sort.by("id", "name");
    		
    		int pageIndex = 1;
    		Pageable pageable = PageRequest.of(pageIndex-1, 2,sort01);
    		Pageable pageable02 = PageRequest.of(pageIndex-1, 2, Direction.ASC, "id");
    		Pageable pageable03 = PageRequest.of(pageIndex-1, 2, Direction.ASC, "id", "name");

# Pageable #

package org.springframework.data.domain;
    import java.util.Optional;
    import org.springframework.util.Assert;
    public interface Pageable { 
    	/** 返回不分页实例 */
    	static Pageable unpaged() { 
    		return Unpaged.INSTANCE;
    	}
    	/** 是否分页 */
    	default boolean isPaged() { 
    		return true;
    	}
    	/** 是否不分页 */
    	default boolean isUnpaged() { 
    		return !isPaged();
    	}
    	/** 页面序号 */
    	int getPageNumber();
    	/** 页面大小 */
    	int getPageSize();
    	/** 通过page和page size计算出的偏移量*/
    	long getOffset();
    	/** 排序 */
    	Sort getSort();
    	/** 当前Sort是否为空Sort对象，不为空返回当前Sort对象，否则返回给定的Sort */
    	default Sort getSortOr(Sort sort) { 
    		Assert.notNull(sort, "Fallback Sort must not be null!");
    		return getSort().isSorted() ? getSort() : sort;
    	}
    	/** 返回下一页 */
    	Pageable next();
    	/** 返回前一页或者第一页 */
    	Pageable previousOrFirst();
    	/** 返回第一页 */
    	Pageable first();
    	/** 是否有前一页 */
    	boolean hasPrevious();
    	/** 用Optional包装分页对象 */
    	default Optional<Pageable> toOptional() { 
    		return isUnpaged() ? Optional.empty() : Optional.of(this);
    	}
    }

# Unpaged #

enum Unpaged implements Pageable { 
    	INSTANCE;
    	public boolean isPaged() { 
    		return false;
    	}
    	public Pageable previousOrFirst() { 
    		return this;
    	}
    	public Pageable next() { 
    		return this;
    	}
    	public boolean hasPrevious() { 
    		return false;
    	}
    	public Sort getSort() { 
    		return Sort.unsorted();
    	}
    	public int getPageSize() { 
    		throw new UnsupportedOperationException();
    	}
    	public int getPageNumber() { 
    		throw new UnsupportedOperationException();
    	}
    	public long getOffset() { 
    		throw new UnsupportedOperationException();
    	}
    	public Pageable first() { 
    		return this;
    	}
    }

# AbstractPageRequest #

public abstract class AbstractPageRequest implements Pageable, Serializable { 
    	private static final long serialVersionUID = 1232825578694716871L;
    	private final int page;
    	private final int size;
    	/** page从0开始计数 */
    	public AbstractPageRequest(int page, int size) { 
    		if (page < 0) { 
    			throw new IllegalArgumentException("Page index must not be less than zero!");
    		}
    		if (size < 1) { 
    			throw new IllegalArgumentException("Page size must not be less than one!");
    		}
    		this.page = page;
    		this.size = size;
    	}
    	public int getPageSize() { 
    		return size;
    	}
    	public int getPageNumber() { 
    		return page;
    	}
    	public long getOffset() { 
    		return (long) page * (long) size;
    	}
    	public boolean hasPrevious() { 
    		return page > 0;
    	}
    	public Pageable previousOrFirst() { 
    		return hasPrevious() ? previous() : first();
    	}
    	public abstract Pageable next();
    	public abstract Pageable previous();
    	public abstract Pageable first();
    }

# PageRequest #

public class PageRequest extends AbstractPageRequest { 
    	private static final long serialVersionUID = -4541509938956089562L;
    	private final Sort sort;
    	/** 废弃方法，代替方法：of(int, int) */
    	@Deprecated
    	public PageRequest(int page, int size) { 
    		this(page, size, Sort.unsorted());
    	}
    	/** 废弃方法，代替方法：of(int, int, Direction, String...) */
    	@Deprecated
    	public PageRequest(int page, int size, Direction direction, String... properties) { 
    		this(page, size, Sort.by(direction, properties));
    	}
    	/** 废弃方法，代替方法：of(int, int, Sort) */
    	@Deprecated
    	public PageRequest(int page, int size, Sort sort) { 
    		super(page, size);
    		this.sort = sort;
    	}
    	/** 创建没有排序的分页请求 */
    	public static PageRequest of(int page, int size) { 
    		return of(page, size, Sort.unsorted());
    	}
    	/** 指定排序的分页请求 */
    	public static PageRequest of(int page, int size, Sort sort) { 
    		return new PageRequest(page, size, sort);
    	}
    	/** 例子： PageRequest.of(0, 15, Direction.ASC, "id", "name"); */
    	public static PageRequest of(int page, int size, Direction direction, String... properties) { 
    		return of(page, size, Sort.by(direction, properties));
    	}
    	public Sort getSort() { 
    		return sort;
    	}
    	public Pageable next() { 
    		return new PageRequest(getPageNumber() + 1, getPageSize(), getSort());
    	}
    	public PageRequest previous() { 
    		return getPageNumber() == 0 ? this : new PageRequest(getPageNumber() - 1, getPageSize(), getSort());
    	}
    	public Pageable first() { 
    		return new PageRequest(0, getPageSize(), getSort());
    	}
    	public String toString() { 
    		return String.format("Page request [number: %d, size %d, sort: %s]", getPageNumber(), getPageSize(), sort);
    	}
    }

# QPageRequest #

public class QPageRequest extends AbstractPageRequest { 
    	private static final long serialVersionUID = 7529171950267879273L;
    	private final QSort sort;
    
    	public QPageRequest(int page, int size) { 
    		this(page, size, QSort.unsorted());
    	}
    	public QPageRequest(int page, int size, OrderSpecifier<?>... orderSpecifiers) { 
    		this(page, size, new QSort(orderSpecifiers));
    	}
    	public QPageRequest(int page, int size, QSort sort) { 
    		super(page, size);
    		this.sort = sort;
    	}
    	public Sort getSort() { 
    		return sort;
    	}
    	public Pageable next() { 
    		return new QPageRequest(getPageNumber() + 1, getPageSize(), sort);
    	}
    	public Pageable previous() { 
    		return new QPageRequest(getPageNumber() - 1, getPageSize(), sort);
    	}
    	@Override
    	public Pageable first() { 
    		return new QPageRequest(0, getPageSize(), sort);
    	}
    }