05. 深入浅出Spring Boot - 数据访问之JDBC（源码分析+代码下载）
阅读目录
一、JDBC是什么？
二、Spring Boot中如何使用JDBC
三、自动配置原理
四、JdbcTemplate
五、配置Swagger用来测试
六、测试
七、报错和解决方案：
Github代码下载：
https://github.com/Jackson0714/study-spring-boot
一、JDBC是什么？
JDBC API 属于Java APIJDBC用于以下几种功能：连接到数据库、执行SQL语句
二、Spring Boot中如何使用JDBC
2.1 创建 Spring Boot Project 时引入 JDBC API 依赖和 MySQL Driver依赖，以及Spring Web依赖（测试时用到）
可以在POM中找到引入的JDBC依赖和mysql依赖：
JDBC 依赖：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>MySql 驱动依赖：
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>2.2 配置数据库连接
新增配置文件：src/main/resources/application.yml
spring:
datasource:
username: root
password: root
url: jdbc:mysql://localhost:3306/study-spring-boot?serverTimezone=UTC&useUnicode=true&zeroDateTimeBehavior=convertToNull&autoReconnect=true&characterEncoding=utf-8
driverClassName: com.mysql.cj.jdbc.Driver注意：com.mysq.jdbc.Driver 被废弃了，需要使用com.mysql.cj.jdbc.Driver
2.3 查看使用的数据源和数据库连接
package com.jackson0714.springboot;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
@SpringBootTest
class Springboot05DataJdbcApplicationTests {
@Autowired
DataSource dataSource; //自动配置数据源，使用yml配置
@Test
void contextLoads() throws SQLException {
System.out.println("数据源：" + dataSource.getClass());
Connection connection = dataSource.getConnection();
System.out.println("数据库连接：" + connection);
connection.close();
}
}
默认数据源：class com.zaxxer.hikari.HikariDataSource
数据库连接：HikariProxyConnection@1335157064 wrapping com.mysql.cj.jdbc.ConnectionImpl@7ff8a9dc
三、自动配置原理
自动配置文件路径：org.springframework.boot.autoconfigure.jdbc
DataSourceConfiguration用来自动导入数据源（根据各种判断）
/**
* Tomcat Pool DataSource configuration.
*/
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
@ConditionalOnMissingBean(DataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource",
matchIfMissing = true)
static class Tomcat {
@Bean
@ConfigurationProperties(prefix = "spring.datasource.tomcat")3.1 自动选择数据源
如果导入了org.apache.tomcat.jdbc.pool.DataSource数据源，并且配置的spring.datasource.type配置的是org.apache.tomcat.jdbc.pool.DataSource，或没配置type也使用tomcat数据源
3.2 HikariDataSource数据源也类似这样判断。
3.3 默认使用tomcat数据源
3.4 默认支持以下数据源
org.apache.tomcat.jdbc.pool、HikariDataSource、org.apache.commons.dbcp23.5 支持自定义数据源
使用DataSourceBuilder创建数据源，利用反射创建响应type的数据源，并且绑定相关属性
/**
* Generic DataSource configuration.
*/
@Configuration(proxyBeanMethods = false)
@ConditionalOnMissingBean(DataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type")
static class Generic {
@Bean
DataSource dataSource(DataSourceProperties properties) {
//使用DataSourceBuilder创建数据源，利用反射创建响应type的数据源，并且绑定相关属性
return properties.initializeDataSourceBuilder().build();
}
}3.6 DataSourceInitializerInvoker 运行脚本
/**
* Bean to handle {@link DataSource} initialization by running {@literal schema-*.sql} on
* {@link InitializingBean#afterPropertiesSet()} and {@literal data-*.sql} SQL scripts on
* a {@link DataSourceSchemaCreatedEvent}.
*
* @author Stephane Nicoll
* @see DataSourceAutoConfiguration
*/
class DataSourceInitializerInvoker implements ApplicationListener<DataSourceSchemaCreatedEvent>, InitializingBean {createSchema() 创建表 （文件名规则 schema-*.sql）
initSchema() 执行数据脚本 （文件名规则 data-*.sql）getScripts() 来获取需要执行的脚本
private List<Resource> getScripts(String propertyName, List<String> resources, String fallback) {
if (resources != null) {
return getResources(propertyName, resources, true);
}
String platform = this.properties.getPlatform();
List<String> fallbackResources = new ArrayList<>();
fallbackResources.add("classpath*:" + fallback + "-" + platform + ".sql");
fallbackResources.add("classpath*:" + fallback + ".sql");
return getResources(propertyName, fallbackResources, false);
}1) fallback = "schema", platform="all",会自动执行根目录下：schema-all.sql 或schema.sql 文件
2) fallback = "data", platform="all",会自动执行根目录下：data-all.sql 或data.sql 文件
isEnabled() 方法判断是否开启了自动执行脚本
有三种模式：NEVER，EMBEDDED（默认），Always
疑问：用EMBEDDED模式返回false，开关关闭，不执行脚本，这是为啥呢？
用Always模式则每次启动spring boot重复执行脚本（创建表脚本都是先判断有没有表，有则删除后重建）
private boolean isEnabled() {
DataSourceInitializationMode mode = this.properties.getInitializationMode();
if (mode == DataSourceInitializationMode.NEVER) {
return false;
}
if (mode == DataSourceInitializationMode.EMBEDDED && !isEmbedded()) {
return false;
}
return true;
}3.7 通过配置文件指定需要执行脚本
schema:
- classpath:department.sql创建出的 department 表
四、JdbcTemplate
JdbcTemplateAutoConfiguration.java 文件 自动注入了JdbcTemplate。（JdbcTemplate用来操作数据库）
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ DataSource.class, JdbcTemplate.class })
@ConditionalOnSingleCandidate(DataSource.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
@EnableConfigurationProperties(JdbcProperties.class)
@Import({ JdbcTemplateConfiguration.class, NamedParameterJdbcTemplateConfiguration.class })
public class JdbcTemplateAutoConfiguration {
}五、配置Swagger用来测试
5.1 pom.xml文件 添加swagger依赖
<!-- swagger -->
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.9.2</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.9.2</version>
</dependency>5.2 添加SwaggerConfig.java文件
package com.jackson0714.springboot.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;
@Configuration
@EnableSwagger2
public class SwaggerConfig {
@Bean
public Docket createRestApi(){
return new Docket(DocumentationType.SWAGGER_2).apiInfo(apiInfo())
.select()
.apis(RequestHandlerSelectors.any())
.paths(PathSelectors.any()).build();
}
private ApiInfo apiInfo(){
return new ApiInfoBuilder()
.title("玩转Spring Boot 接口文档")
.description("This is a restful api document of Spring Boot.")
.version("1.0")
.build();
}
}5.3 访问Swagger文档
http://localhost:8081/swagger-ui.html
回到顶部
六、测试
6.1 新增部门
@ApiOperation(value = "1.新增部门")
@ApiImplicitParams({
@ApiImplicitParam(name = "name", value = "部门名称")
})
@PostMapping("/create")
public int createDepartment(@RequestParam String name) {
String sql = String.format("insert into department(departmentName) value('%s')", name);
int result = jdbcTemplate.update(sql);
return result;
}
表记录
6.2 查询所有部门
@ApiOperation(value = "2.查询所有部门")
@GetMapping("/getAllDepartment")
public List<Map<String, Object>> getAllDepartment() {
List<Map<String, Object>> list = jdbcTemplate.queryForList("select * from department");
return list;
}6.3 根据id查询某个部门
@ApiOperation(value = "3.根据id查询某个部门")
@ApiImplicitParams({
@ApiImplicitParam(name = "id", value = "需要查询的部门id")
})
@GetMapping("/{id}")
public Map<String, Object> getDepartmentById(@PathVariable Long id) {
String sql = "select * from department where id = " + id;
List<Map<String, Object>> list = jdbcTemplate.queryForList(sql);
return list.get(0);
}6.4 根据id更新部门名称
@ApiOperation(value = "根据id更新部门名称")
@ApiImplicitParams({
@ApiImplicitParam(name = "id", value = "需要更新的部门id"),
@ApiImplicitParam(name = "name", value = "需要更新的部门名称")
})
@PostMapping("/update")
public int updateDepartmentById(@RequestParam Long id, @RequestParam String name) {
String sql = String.format("update department set departmentName = '%s' where id = %d", name, id);
int result = jdbcTemplate.update(sql);
return result;
}6.5 根据id删除部门
@ApiOperation(value = "根据id删除部门")
@ApiImplicitParams({
@ApiImplicitParam(name = "id", value = "需要删除的部门id")
})
@PostMapping("/delete")
public int deleteDepartment(@RequestParam Long id) {
String sql = String.format("delete from department where id = %d", id);
int result = jdbcTemplate.update(sql);
return result;
}七、报错和解决方案：
7.1 问题1
java.sql.SQLException:null, message from server: "Host 'Siri' is not allowed to connect to this MySQL server"
解决方案：
执行命令：
use mysql;
select host from user;
update user set host = '%' where user = 'root'执行结果：
Query OK, 1 row affected如下图所示：
7.2 问题2
Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.
解决方案：
配置spring.datasource.url 时，增加参数：serverTimezone=UTC
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