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SpringbootJPA分页PageRequest过时 SpringbootJPA分页 PageRequest过时的替代方法

伟大的格尔夫斯 人气:0
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1. 原因

最近学习spring data JPA 时候要用到分页功能，但是发现网上所有教程都是通过new PageRequest()方法解决分页，实际使用中发现已经过时

2. 解决方案

替代的方法是不要new PageRequest，而是直接用 PageRequest.of这个方法 根据你的需求选择入参

3. 对比

原来：

@Override
@Transactional(readOnly = true)  // 只读事务
public Page<People> getPage(Integer pageNum, Integer pageLimit) {
        Pageable pageable =new PageRequest(pageNum - 1,pageLimit);
        return emr.findAll(pageable);
}

现在：

@Override
@Transactional(readOnly = true)  // 只读事务
public Page<People> getPage(Integer pageNum, Integer pageLimit) {
　　　　Pageable pageable =PageRequest.of(pageNum - 1,pageLimit);
　　　　return emr.findAll(pageable)；
}

pageRequest随着spring版本的更新变动

2x版本：

/*
 * Copyright 2008-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.domain;
import org.springframework.data.domain.Sort.Direction;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
 * Basic Java Bean implementation of {@code Pageable}.
 *
 * @author Oliver Gierke
 * @author Thomas Darimont
 */
public class PageRequest extends AbstractPageRequest {
	private static final long serialVersionUID = -4541509938956089562L;
	private final Sort sort;
	/**
	 * Creates a new {@link PageRequest} with sort parameters applied.
	 *
	 * @param page zero-based page index, must not be negative.
	 * @param size the size of the page to be returned, must be greater than 0.
	 * @param sort must not be {@literal null}, use {@link Sort#unsorted()} instead.
	 */
	protected PageRequest(int page, int size, Sort sort) {
		super(page, size);
		Assert.notNull(sort, "Sort must not be null!");
		this.sort = sort;
	}
	/**
	 * Creates a new unsorted {@link PageRequest}.
	 *
	 * @param page zero-based page index, must not be negative.
	 * @param size the size of the page to be returned, must be greater than 0.
	 * @since 2.0
	 */
	public static PageRequest of(int page, int size) {
		return of(page, size, Sort.unsorted());
	}
	/**
	 * Creates a new {@link PageRequest} with sort parameters applied.
	 *
	 * @param page zero-based page index.
	 * @param size the size of the page to be returned.
	 * @param sort must not be {@literal null}, use {@link Sort#unsorted()} instead.
	 * @since 2.0
	 */
	public static PageRequest of(int page, int size, Sort sort) {
		return new PageRequest(page, size, sort);
	}
	/**
	 * Creates a new {@link PageRequest} with sort direction and properties applied.
	 *
	 * @param page zero-based page index, must not be negative.
	 * @param size the size of the page to be returned, must be greater than 0.
	 * @param direction must not be {@literal null}.
	 * @param properties must not be {@literal null}.
	 * @since 2.0
	 */
	public static PageRequest of(int page, int size, Direction direction, String... properties) {
		return of(page, size, Sort.by(direction, properties));
	}
	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#getSort()
	 */
	public Sort getSort() {
		return sort;
	}
	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#next()
	 */
	@Override
	public Pageable next() {
		return new PageRequest(getPageNumber() + 1, getPageSize(), getSort());
	}
	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.AbstractPageRequest#previous()
	 */
	@Override
	public PageRequest previous() {
		return getPageNumber() == 0 ? this : new PageRequest(getPageNumber() - 1, getPageSize(), getSort());
	}
	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#first()
	 */
	@Override
	public Pageable first() {
		return new PageRequest(0, getPageSize(), getSort());
	}
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(@Nullable Object obj) {
		if (this == obj) {
			return true;
		}
		if (!(obj instanceof PageRequest)) {
			return false;
		}
		PageRequest that = (PageRequest) obj;
		return super.equals(that) && this.sort.equals(that.sort);
	}
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 */
	@Override
	public int hashCode() {
		return 31 * super.hashCode() + sort.hashCode();
	}
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return String.format("Page request [number: %d, size %d, sort: %s]", getPageNumber(), getPageSize(), sort);
	}
}

1x版本：

/*
 * Copyright 2008-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.domain;
import org.springframework.data.domain.Sort.Direction;
/**
 * Basic Java Bean implementation of {@code Pageable}.
 * 
 * @author Oliver Gierke
 * @author Thomas Darimont
 */
public class PageRequest extends AbstractPageRequest {
	private static final long serialVersionUID = -4541509938956089562L;
	private final Sort sort;
	/**
	 * Creates a new {@link PageRequest}. Pages are zero indexed, thus providing 0 for {@code page} will return the first
	 * page.
	 * 
	 * @param page zero-based page index.
	 * @param size the size of the page to be returned.
	 */
	public PageRequest(int page, int size) {
		this(page, size, null);
	}
	/**
	 * Creates a new {@link PageRequest} with sort parameters applied.
	 * 
	 * @param page zero-based page index.
	 * @param size the size of the page to be returned.
	 * @param direction the direction of the {@link Sort} to be specified, can be {@literal null}.
	 * @param properties the properties to sort by, must not be {@literal null} or empty.
	 */
	public PageRequest(int page, int size, Direction direction, String... properties) {
		this(page, size, new Sort(direction, properties));
	}
	/**
	 * Creates a new {@link PageRequest} with sort parameters applied.
	 * 
	 * @param page zero-based page index.
	 * @param size the size of the page to be returned.
	 * @param sort can be {@literal null}.
	 */
	public PageRequest(int page, int size, Sort sort) {
		super(page, size);
		this.sort = sort;
	}
	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#getSort()
	 */
	public Sort getSort() {
		return sort;
	}
	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#next()
	 */
	public Pageable next() {
		return new PageRequest(getPageNumber() + 1, getPageSize(), getSort());
	}
	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.AbstractPageRequest#previous()
	 */
	public PageRequest previous() {
		return getPageNumber() == 0 ? this : new PageRequest(getPageNumber() - 1, getPageSize(), getSort());
	}
	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Pageable#first()
	 */
	public Pageable first() {
		return new PageRequest(0, getPageSize(), getSort());
	}
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(final Object obj) {
		if (this == obj) {
			return true;
		}
		if (!(obj instanceof PageRequest)) {
			return false;
		}
		PageRequest that = (PageRequest) obj;
		boolean sortEqual = this.sort == null ? that.sort == null : this.sort.equals(that.sort);
		return super.equals(that) && sortEqual;
	}
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 */
	@Override
	public int hashCode() {
		return 31 * super.hashCode() + (null == sort ? 0 : sort.hashCode());
	}
	/* 
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return String.format("Page request [number: %d, size %d, sort: %s]", getPageNumber(), getPageSize(),
				sort == null ? null : sort.toString());
	}
}

2x版本常用创建实例方式：

调用静态方法

在这里插入图片描述

从源码中看到2x版本的构造器是使用protected修饰的,所有无法通过new的方式去创建实例,只能通过调用static修饰的方法进行创建。

1x版本常用创建实例方式：

直接调用构造器即可

在这里插入图片描述

因为1x版本使用的是public修饰的构造器，所以可以直接使用构造器创建实例。

刚使用spring自带的分页工具Pageable入的坑，自己记录一下，希望能给大家一个参考，也希望大家多多支持。

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