[JAVA]逻辑分页与物理分页
code：mybatis+springboot
解释
逻辑分页
逻辑分页并不是返回分页结果，而是直接返回全部数据，再通过代码获取分页数据。
物理分页
使用mysql的limit关键字，直接返回分页结果。
编码
sql
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL,
`age` int(11) DEFAULT NULL,
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Compact;
-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '测试1', 11);
INSERT INTO `student` VALUES (2, '测试2', 22);
INSERT INTO `student` VALUES (3, '测试3', 14);
INSERT INTO `student` VALUES (4, '测试4', 16);
INSERT INTO `student` VALUES (5, '测试5', 32);
INSERT INTO `student` VALUES (6, '测试6', 23);
SET FOREIGN_KEY_CHECKS = 1;对应的实体类
public class Student {
//构造
private int id;
private String name;
private int age;
//get set
}pom.xml
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>mybatis</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>mybatis</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<!--注意：如果xml文件不放到resources下，那么需要配置以下代码，不然target下找不到-->
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.*</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
<include>**/*.yml</include>
<include>**/*.properties</include>
</includes>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>application.properties
#jdbc驱动
spring.datasource.driverClassName = com.mysql.cj.jdbc.Driver
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai
spring.datasource.username = ****
spring.datasource.password = ****
#mybatis
#xml地址
mybatis.mapper-locations=classpath:com/example/mybatis/dao/mapping/**.xml
#控制台打印sql
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl结构
Controller –> service –> dao –>xml
controller
@RestController
public class StudentController {
@Autowired
private SutndentServiceImpl studentService;
/**
* 物理分页
*/
@GetMapping("physical-paging")
public Object getList1(@RequestParam(value = "start", required = false, defaultValue = "1") int start,
@RequestParam(value = "limit", required = false, defaultValue = "3") int limit) {
List<Student> list = studentService.physicalPaging(start, limit);
return list;
}
/**
* 逻辑分页
*/
@GetMapping("logical-paging")
public Object getList2(@RequestParam(value = "start", required = false, defaultValue = "1") int start,
@RequestParam(value = "limit", required = false, defaultValue = "3") int limit) {
List<Student> list = studentService.logicalPaging(start, limit);
return list;
}
}service+实现类
public interface StudentService {
/**
* 物理分页
*
* @param start 起始页
* @param limit 每页条数
* @return
*/
List<Student> physicalPaging(int start, int limit);
/**
* 逻辑分页
*
* @param start
* @param limit
* @return
*/
List<Student> logicalPaging(int start, int limit);
}注意：实现类的@Service
@Service
public class SutndentServiceImpl implements StudentService {
@Autowired
private StudentDao studentDao;
@Override
public List<Student> physicalPaging(int start, int limit) {
//这里是分页的关键
if (start < 1) {
start = 1;
} else {
start = (start - 1) * limit;
}
List<Student> list = studentDao.getList(start, limit);
return list;
}
@Override
public List<Student> logicalPaging(int start, int limit) {
if (start < 1) {
start = 1;
}
List<Student> list = studentDao.getAllList();
if((start-1)*limit > list.size()){
return Collections.emptyList();
}
return list.subList((start - 1) * limit, ((start * limit) > list.size() ? list.size() : (start * limit)));
}
}
dao
注意：类上的@Mapper,文件多时可选择启动类上设置@MapperScan，这样不需要每个mapper加注解。
@Mapper
public interface StudentDao {
/**
* 注意:1、有@Mapper注解 2、一个以上的参数需要加@param
*
* @param start 起始页
* @param limit 每页多少条
* @return
*/
List<Student> getList(@Param("start") int start, @Param("limit") int limit);
/**
* 获取全部数据
*
* @return
*/
List<Student> getAllList();
}
XML映射文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.mybatis.dao.StudentDao">
<!-- 通用查询映射结果 -->
<resultMap id="BaseResultMap" type="com.example.mybatis.baen.Student">
<id column="id" property="id"/>
<result column="name" property="name"/>
<result column="age" property="age"/>
</resultMap>
<!-- 通用查询结果列 -->
<sql id="Base_Column_List">
id, name, age
</sql>
<select id="getList" resultType="com.example.mybatis.baen.Student">
select
<include refid="Base_Column_List"/>
from student limit #{start},#{limit}
</select>
<select id="getAllList" resultType="com.example.mybatis.baen.Student">
select
<include refid="Base_Column_List"/>
from student
</select>
</mapper>测试
逻辑分页接口测试
http://127.0.0.1:8080/logical-paging?start=1&limit=2
---
[
{
"id": 1,
"name": "测试1",
"age": 11
},
{
"id": 2,
"name": "测试2",
"age": 22
}
]物理分页接口测试
http://127.0.0.1:8080/physical-paging?start=1&limit=2
---
[
{
"id": 1,
"name": "测试1",
"age": 11
},
{
"id": 2,
"name": "测试2",
"age": 22
}
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文章标题:[JAVA]逻辑分页与物理分页
文章字数:1.4k
本文作者:周信
发布时间:2020-01-05, 13:49:29
最后更新:2023-05-03, 10:25:35
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