代码改变世界

Springboot整合Mybatis开发入门

2021-04-23 21:41  Hungs  阅读(242)  评论(0)    收藏  举报

创建Springboot项目

首先，通过idea创建一个springboot基础项目。

 创建成功后，运行程序看下是否正常启动。

配置数据库信息并验证数据库连接成功

在pom.xml中引入数据库依赖

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

在application.yml或者application.properties文件中配置数据库信息，如下是yml的配置：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test?characterEncoding=UTF-8
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver

在Test类中，实现数据库连接测试：

@SpringBootTest
class Chapter01ApplicationTests {
    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
            System.out.println(dataSource.getConnection().toString());
    }
}

运行Chapter01ApplicationTests测试类，发现项目报错：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.hungs.Chapter01ApplicationTests': Unsatisfied dependency expressed through field 'dataSource'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'javax.sql.DataSource' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:660) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1413) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:399) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:119) ~[spring-test-5.3.6.jar:5.3.6]
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83) ~[spring-test-5.3.6.jar:5.3.6]
    at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:43) ~[spring-boot-test-autoconfigure-2.4.5.jar:2.4.5]
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:244) ~[spring-test-5.3.6.jar:5.3.6]
    at org.springframework.test.context.junit.jupiter.SpringExtension.postProcessTestInstance(SpringExtension.java:138) [spring-test-5.3.6.jar:5.3.6]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$6(ClassBasedTestDescriptor.java:350) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.executeAndMaskThrowable(ClassBasedTestDescriptor.java:355) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$7(ClassBasedTestDescriptor.java:350) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_92]
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) ~[na:1.8.0_92]
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374) ~[na:1.8.0_92]
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_92]
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_92]
    at java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312) ~[na:1.8.0_92]
    at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:743) ~[na:1.8.0_92]
    at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:742) ~[na:1.8.0_92]
    at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580) ~[na:1.8.0_92]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstancePostProcessors(ClassBasedTestDescriptor.java:349) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$instantiateAndPostProcessTestInstance$4(ClassBasedTestDescriptor.java:270) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:269) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$2(ClassBasedTestDescriptor.java:259) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at java.util.Optional.orElseGet(Optional.java:267) ~[na:1.8.0_92]
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$3(ClassBasedTestDescriptor.java:258) [junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:31) ~[junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:101) ~[junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:100) ~[junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:65) ~[junit-jupiter-engine-5.7.1.jar:5.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$1(NodeTestTask.java:111) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:111) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:79) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at java.util.ArrayList.forEach(ArrayList.java:1249) ~[na:1.8.0_92]
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at java.util.ArrayList.forEach(ArrayList.java:1249) ~[na:1.8.0_92]
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51) ~[junit-platform-engine-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75) ~[junit-platform-launcher-1.7.1.jar:1.7.1]
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:69) ~[junit5-rt.jar:na]
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) ~[junit-rt.jar:na]
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230) ~[junit-rt.jar:na]
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58) ~[junit-rt.jar:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'javax.sql.DataSource' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1790) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1346) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1300) ~[spring-beans-5.3.6.jar:5.3.6]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657) ~[spring-beans-5.3.6.jar:5.3.6]
    ... 72 common frames omitted

从错误上来乍一看好像是没有引入mysql数据库依赖，但是在pom.xml中明明已经引入了，且Chapter01ApplicationTests类中也没有编译报错。检查后发现，maven依赖引入没有生效。

 点击左上角的reload,依赖加载出来了

 重启之后，还是报错，网上的大概意思是说需要一个私有的DataSource，https://www.it1352.com/742237.html，感觉改动的东西很多，与初衷不符（初衷是整合mybatis进行简单查询）所以，先试着导入mybatis的依赖：

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.3</version>
</dependency>

发现重启程序发现能够正常运行，并连接数据库成功。如下图：

 得出结论：mybaits中估计引入了与jdbc相关的依赖包，通过查找不难发现，mybatis-spring-boot-starter中导入了spring-boot-starter-jdbc依赖包，那么为了验证确实是spring-boot-starter-jdbc可以解决遇到的问题，将mybatis-spring-boot-starter删除，换成spring-boot-starter-jdbc的依赖，重启程序，为了避免缓存什么的影响，先clean下。发现程序运行正常，数据库连接能够获得。

新建POJO类

新建一个pojo文件夹，再其下建People类

@Data
@NoArgsConstructor
@AllArgsConstructor
public class People {
    private int id;
    private String name;
    private int age;
    private String phone;
    private String address;
    private String hobby;
}

@Data @NoArgsConstructor @AllArgsConstructor 这些注解，需要引入lombok的依赖，关于lombok：https://www.jianshu.com/p/2543c71a8e45

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.20</version>
</dependency>

新建Mapper类，写测试接口

新建一个mapper文件夹，在其下建PeopleMapper的接口类

@Mapper
@Repository
public interface PeopleMapper {

    // 通过ID获取人的对象
    People getPeopleByID(int id);
}

@Mapper是mybatis的注解，@Repository是spring的注解，为了使IOC容器装载。

新建一个controller文件夹，在其下建PeopleController类

@RestController
public class PeopleController {

    @Autowired
    private PeopleMapper peopleMapper;

    @RequestMapping("/get")
    public String getPeople(){
        return peopleMapper.getPeopleByID(1).toString();
    }
}

其中mysql数据库中插入了几条语句，这是项目开始之前可以做的，截图如下：

配置mybatis-config.xml，配置接口对应mapper和sql语句

在resources下新建mapper文件夹，新建一个mybatis-config.xml的文件，打开mybatis中文官网：https://mybatis.net.cn/getting-started.html 找到如下配置，直接复制到文件中，并进行修改，注意：namespace对应PeopleMapper的全路径。

<?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.hungs.mapper.PeopleMapper">
    <select id="getPeopleByID" resultType="People">
        select * from people where id = #{id}
    </select>
</mapper>

配置mapper于mybatis-config.xml的映射

在application.yml中配置mybatis的文件路径和扫描路径

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test?characterEncoding=UTF-8
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis:
  mapper-locations: classpath:mapper/*.xml
  type-aliases-package: com.hungs.pojo

启动项目，浏览器请求 http://localhost:8080/get，返回结果。