Spring Boot笔记-JPA分页（后端分页）

小咪咪 2023-01-17 03:17 203阅读 0赞

数据库内容如下：

![20210426181617979.png][]

使用Pageable即可。

Maven如下：

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>org.example</groupId>
        <artifactId>JPAPageable</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <dependencies>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
                <version>2.1.10.RELEASE</version>
            </dependency>
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.10</version>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <version>2.1.10.RELEASE</version>
            </dependency>
    
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.73</version>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
                <version>2.1.10.RELEASE</version>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.37</version>
                <scope>runtime</scope>
            </dependency>
        </dependencies>
    
    </project>

ORM的对象是这样的TestDemo.java：

package cn.it1995.object;
    
    import javax.persistence.*;
    
    @Entity
    @Table(name = "test_demo", schema = "TESTDB", catalog = "")
    public class TestDemo {
        private long id;
        private String value1;
        private Integer value2;
    
        @Id
        @Column(name = "id")
        public long getId() {
            return id;
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        @Basic
        @Column(name = "value_1")
        public String getValue1() {
            return value1;
        }
    
        public void setValue1(String value1) {
            this.value1 = value1;
        }
    
        @Basic
        @Column(name = "value_2")
        public Integer getValue2() {
            return value2;
        }
    
        public void setValue2(Integer value2) {
            this.value2 = value2;
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
    
            TestDemo testDemo = (TestDemo) o;
    
            if (id != testDemo.id) return false;
            if (value1 != null ? !value1.equals(testDemo.value1) : testDemo.value1 != null) return false;
            if (value2 != null ? !value2.equals(testDemo.value2) : testDemo.value2 != null) return false;
    
            return true;
        }
    
        @Override
        public int hashCode() {
            int result = (int) (id ^ (id >>> 32));
            result = 31 * result + (value1 != null ? value1.hashCode() : 0);
            result = 31 * result + (value2 != null ? value2.hashCode() : 0);
            return result;
        }
    }

仓库如下：

TestDemoRepository.java

package cn.it1995.repository;
    
    import cn.it1995.object.TestDemo;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.stereotype.Repository;
    
    @Repository
    public interface TestDemoRepository extends JpaRepository<TestDemo, Long> {
    }

service端如下：

TestDemoService.java

package cn.it1995.service;
    
    import cn.it1995.object.TestDemo;
    import cn.it1995.repository.TestDemoRepository;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.data.domain.Page;
    import org.springframework.data.domain.PageRequest;
    import org.springframework.data.domain.Pageable;
    import org.springframework.stereotype.Service;
    
    
    @Service
    public class TestDemoService {
    
        @Autowired
        private TestDemoRepository testDemoRepository;
    
        public Page<TestDemo> listAll(Integer pageNum){
    
            Pageable pageable = PageRequest.of(pageNum - 1, 10);
            Page<TestDemo> all = testDemoRepository.findAll(pageable);
            return all;
        }
    }

关键的就是这个，分页我们需要的，一共多少条数据，当前是第几页：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxNzg0NDI3NjE_size_16_color_FFFFFF_t_70][]

这里可以看到，当前page为0，当前总数是37，这样就是后端分页了。将其返回值封装下，就可以给前端了。

[20210426181617979.png]: /images/20221022/8d798ac083ef48a7bad8ee08a28706b1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxNzg0NDI3NjE_size_16_color_FFFFFF_t_70]: /images/20221022/76af0df79a214bc8a864be954969a7f2.png