10分钟进阶SpringBoot - 05. 数据访问之JDBC

github代码下载

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：[email protected] wrapping [email protected]

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.dbcp2

3.5 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 {

}

我们用Swagger的方式来测试

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

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;
}

报错：

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：

问题2

Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value ‘?й???????‘ 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

原文地址：https://www.cnblogs.com/jackson0714/p/spring-boot-05-jdbc.html