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這篇文章主要介紹Java中如何使用MyBatis-Plus操作數據庫，文中介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們一定要看完！
MyBatis-Plus (opens new window)（簡稱 MP）是一個 MyBatis (opens new window)的增強工具，在 MyBatis 的基礎上只做增強不做改變，為簡化開發、提高效率而生。
MyBatis可以直接在xml中通過SQL語句操作數據庫，很靈活。但其操作都要通過SQL語句進行，就必須寫大量的xml文件，很麻煩。mybatis-plus就很好的解決了這個問題。
MyBatis-Plus 官方文檔
這里我用的數據庫是mysql8，新建test數據庫，并創建user表
建表語句
SET NAMES utf8mb4; SET FOREIGN_KEY_CHECKS = 0; -- ---------------------------- -- Table structure for user -- ---------------------------- DROP TABLE IF EXISTS `user`; CREATE TABLE `user` ( `id` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '主鍵', `name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名', `age` int(0) NULL DEFAULT NULL COMMENT '年齡', `address` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '地址', PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; SET FOREIGN_KEY_CHECKS = 1;
引入依賴
這里我用的數據庫是mysql8
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.6.3</version> <relativePath/> </parent> <dependencies> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-test</artifactId> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> </dependency> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.5.1</version> </dependency> <!--Druid連接池--> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.1.9</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.25</version> </dependency> </dependencies>
分別創建application.yml及application-dev.yml文件
application.yml
# Spring配置 spring: # 環境設置 profiles: active: dev # 模板引擎 thymeleaf: mode: HTML encoding: utf-8 # 禁用緩存 cache: false # 服務模塊 devtools: restart: # 熱部署開關 enabled: true
application-dev.yml
# 開發環境配置 server: # 服務器的HTTP端口，默認為80 port: 8081 spring: datasource: type: com.alibaba.druid.pool.DruidDataSource driver-class-name: com.mysql.cj.jdbc.Driver druid: url: jdbc:mysql://localhost:3307/test?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8 username: root password: 123456 initial-size: 5 min-idle: 10 max-active: 20 max-wait: 60000 time-between-eviction-runs-millis: 60000 min-evictable-idle-time-millis: 300000 validation-query: select 'x' test-while-idle: true test-on-borrow: false test-on-return: false pool-prepared-statements: true max-open-prepared-statements: 50 max-pool-prepared-statement-per-connection-size: 20
編寫實體類User.java,這里用到lombok
@Data
public class User {
private String id;
private String name;
private Integer age;
private String address;
}創建mapper文件夾,并編寫 Mapper 類 UserMapper.java
public interface UserMapper extends BaseMapper<User> {
}在 Spring Boot 啟動類中添加 @MapperScan 注解，掃描 Mapper 文件夾：
@SpringBootApplication
@MapperScan("com.mybatisplus.mapper")
public class MainApplication {
public static void main(String[] args)
{
SpringApplication.run(MainApplication.class, args);
}
}添加測試類，進行功能測試：
@Autowired
private UserMapper userMapper;
@Test
public void testInsert() {
System.out.println(("----- insert method test ------"));
User user = new User();
// 自動生成主鍵,例如550E8400-E29B-11D4-A716-446655440000
String id = UUID.randomUUID().toString();
String replaceAll = id.replaceAll("-", "");
//550E8400E29B11D4A716446655440000
user.setId(replaceAll);
user.setName("張三");
user.setAge(21);
user.setAddress("北京市海淀區");
int insert = userMapper.insert(user);
if(insert>0){
System.out.println("插入成功："+user);
}else{
System.out.println("插入失敗！");
}
}
@Autowired
private UserMapper userMapper;
@Test
public void testSelect() {
System.out.println(("----- selectAll method test ------"));
List<User> userList = userMapper.selectList(null);
userList.forEach(System.out::println);
}
刪除姓名等于“張三”的記錄
@Autowired
private UserMapper userMapper;
@Test
public void testDelete() {
System.out.println(("----- delete method test ------"));
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
User user = new User();
user.setName("張三");
wrapper.eq(User::getName, user.getName());
int delete = userMapper.delete(wrapper);
if(delete>0){
System.out.println("刪除成功："+user);
}else{
System.out.println("刪除失敗！");
}
}
修改前先執行下插入
修改還可以用userMapper.updateById(T entity)方法來修改，傳入一個實體類
@Autowired
private UserMapper userMapper;
@Test
public void testUpdate() {
System.out.println(("----- update method test ------"));
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
User user = new User();
user.setName("張三");
wrapper.eq(User::getName, user.getName());
User userNew = new User();
userNew.setName("李四");
int update = userMapper.update(userNew, wrapper);
if(update>0){
System.out.println("修改成功："+user);
}else{
System.out.println("修改失敗！");
}
}
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