SpringbootJPA分頁 PageRequest過時(shí)的替代方法
更新時(shí)間：2021年06月15日 08:39:35 作者：偉大的格爾夫斯
這篇文章主要介紹了SpringbootJPA分頁 PageRequest過時(shí)的替代方法，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教
1. 原因
最近學(xué)習(xí)spring data JPA 時(shí)候要用到分頁功能，但是發(fā)現(xiàn)網(wǎng)上所有教程都是通過new PageRequest()方法解決分頁，實(shí)際使用中發(fā)現(xiàn)已經(jīng)過時(shí)
2. 解決方案
替代的方法是不要new PageRequest，而是直接用 PageRequest.of這個(gè)方法 根據(jù)你的需求選擇入?yún)?/p>
3. 對(duì)比
原來：
@Override
@Transactional(readOnly = true) // 只讀事務(wù)
public Page<People> getPage(Integer pageNum, Integer pageLimit) {
Pageable pageable =new PageRequest(pageNum - 1,pageLimit);
return emr.findAll(pageable);
}
現(xiàn)在：
@Override
@Transactional(readOnly = true) // 只讀事務(wù)
public Page<People> getPage(Integer pageNum, Integer pageLimit) {
Pageable pageable =PageRequest.of(pageNum - 1,pageLimit);
return emr.findAll(pageable)；
}
pageRequest隨著spring版本的更新變動(dòng)
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版本常用創(chuàng)建實(shí)例方式：
調(diào)用靜態(tài)方法
從源碼中看到2x版本的構(gòu)造器是使用protected修飾的,所有無法通過new的方式去創(chuàng)建實(shí)例,只能通過調(diào)用static修飾的方法進(jìn)行創(chuàng)建。
1x版本常用創(chuàng)建實(shí)例方式：
直接調(diào)用構(gòu)造器即可
因?yàn)?x版本使用的是public修飾的構(gòu)造器，所以可以直接使用構(gòu)造器創(chuàng)建實(shí)例。
剛使用spring自帶的分頁工具Pageable入的坑，自己記錄一下，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。
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