1、数据源配置
1.1、添加POM依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
1.2、数据源的默认配置
由于只添加了spring-boot-starter-jdbc
pom依赖所以默认使用的是org.apache.tomcat.jdbc.pool.DataSource
数据源, 数据源属性的相关配置在org.springframework.boot.autoconfigure.jdbc.DataSourceProperties
里面。
2、集成JPA
2.1、编写实体类
@Entity
@Table(name = "tb_user")
@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler"})
public class User {
@Id
@GeneratedValue
private Integer id;
@Column(name = "last_name", length = 50)
private String lastName;
@Column
private String email;
//省略getter/setter方法
}
说明:编写实体类和数据表进行映射,配置好表字段和实体属性的映射关系
- 使用
@Entity
告诉JPA
这是一个实体类 - 使用
@Table
指定和哪个数据表对应,如果省略默认表名就是类名小写 - 使用
@Id
指定该属性对应于表的主键,使用@GeneratedValue
指定主键的生成方式 - 使用
@Cloumn
指定该属性对应于表的具体字段,默认情况下属性名就是字段名
注意:如果未使用@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler"})
将会出现以下错误
"Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.hanson.entity.User_$$_jvstf1d_0[\"handler\"])"
出现错误的原因:
hibernate延时加载因为jsonplugin用的是Java的内审机制.hibernate会给被管理的pojo加入一个hibernateLazyInitializer属性,jsonplugin会把hibernateLazyInitializer也拿出来操作,并读取里面一个不能被反射操作的属性就产生了这个异常.
2.2、编写Dao接口
public interface UserRepository extends JpaRepository<User,Integer>{
}
JpaRepository
封装了对数据库(表)的简单操作
2.3、JPA的配置
spring:
# 数据源基本属性配置
datasource:
url: jdbc:mysql://localhost:3306/jpa
username: root
password: root
driver-class-name: com.mysql.jdbc.Driver
# jpa基本配置
jpa:
hibernate:
# 创建或更新表
ddl-auto: update
# 控制台显示SQL
show-sql: true
3、集成MyBatis
3.1、添加MyBatis依赖
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.2</version>
</dependency>
该依赖引入了mybatis
、mybatis-spring
整合包、mybatis-spring-boot-autoconfigure
3.2、数据源配置
spring:
datasource:
username: root
password: root
url: jdbc:mysql://localhost:3306/springboot
driver-class-name: com.mysql.jdbc.Driver
# 打印sql
logging:
level:
com.hanson.mapper : debug
3.3、创建表
--用户表
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(32) NOT NULL COMMENT '用户名称',
`birthday` date DEFAULT NULL COMMENT '生日',
`sex` char(1) DEFAULT NULL COMMENT '性别',
`address` varchar(256) DEFAULT NULL COMMENT '地址',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8;
--订单表
DROP TABLE IF EXISTS `orders`;
CREATE TABLE `orders` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11) NOT NULL COMMENT '下单用户id',
`number` varchar(32) NOT NULL COMMENT '订单号',
`createtime` datetime NOT NULL COMMENT '创建订单时间',
`note` varchar(100) DEFAULT NULL COMMENT '备注',
PRIMARY KEY (`id`),
KEY `FK_orders_1` (`user_id`),
CONSTRAINT `FK_orders_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
3.3、创建实体类
public class User {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
//省略getter/setter方法
}
public class Order {
private Integer id;
private Integer userId;
private String number;
private Date createTime;
private String note;
//省略getter/setter方法
}
3.4、基于注解开发
3.4.1、Mapper接口
@Mapper
public interface OrderMapper {
@Select("SELECT * from orders where id = #{id}")
Order getOrderById(Integer id);
@Delete("DELETE FROM orders where id = #{id}")
int delOrderById(Integer id);
@Options(useGeneratedKeys = true, keyProperty = "id")
@Insert("insert into orders(user_id,number,createtime,note)values(#{userId},#{number},#{createTime},#{note})")
int add(Order order);
@Update("update orders set user_id = #{userId}, number=#{number},note=#{note} where id=#{id}")
int update(Order order);
}
使用@Mapper
表明这是一个映射器,映射器需要被MyBatis管理。 当接口有很多在每一个Mapper接口上添加@Mapper
也很麻烦,所以需要用到一个Mapper接口扫描器@MapperScan
3.4.2、Mapper接口扫描器
@SpringBootApplication
@MapperScan({"com.hanson.mapper"})
public class MybatisApplication {
public static void main(String[] args) {
SpringApplication.run(MybatisApplication.class, args);
}
}
3.5、基于XML开发
3.5.1、Mapper接口
public interface UserMapper {
User getUserById(Integer id);
int updateUser(User user);
}
Mapper
接口依然需要被Mybatis
管理所以要么是使用@Mapper
注解要么使用Mapper接口扫描器@MapperScan
3.5.2、Mapper.xml
<?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.hanson.mapper.UserMapper">
<select id="getUserById" resultType="com.hanson.bean.User">
SELECT *
FROM user
WHERE id = #{id}
</select>
<update id="updateUser">
UPDATE user
SET username = #{username},
birthday = #{birthday},
sex = #{sex},
address = #{address}
WHERE
id = #{id}
</update>
</mapper>
3.5.3、MyBatis核心配置文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
</configuration>
3.5.4、配置MyBatis
spring:
datasource:
username: root
password: root
url: jdbc:mysql://localhost:3306/springboot
driver-class-name: com.mysql.jdbc.Driver
# 打印sql
logging:
level:
com.hanson.mapper : debug
mybatis:
# mybatis全局配置
config-location: classpath:mybatis/mybatisConfig.xml
# 配置mapper接口映射文件
mapper-locations: classpath:mybatis/mapper/*.xml
3.6、MyBatis定制
3.6.1、基于XML定制
在mybtais的核心配置文件中自定义配置自定义内容,可以配置Mybatis的运行行为
3.6.2、基于配置文件定制
参考MyBatis的属性配置类在application.properties或者aplication.yml配置
3.6.3、基于Java代码定制
@SpringBootConfiguration
public class MybatisConfiguration {
@Bean
public ConfigurationCustomizer configurationCustomizer() {
return (configuration) -> {
//别名注册器
TypeAliasRegistry typeAliasRegistry = configuration.getTypeAliasRegistry();
//mapper接口注册器
MapperRegistry mapperRegistry = configuration.getMapperRegistry();
//类型处理器
TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
//...
};
}
}
推荐第二种或者第三种