问题描述
在应用MyBatis时,使用对象关系映射,将对象和Aliase映射起来。
在Mybatis的文档明确写出,如果你没有明确定义实体类的Aliase,框架会自动将Class Name自动作为别名。
那么问题来了,当使用java -jar xxx.jar&启动的时候,会报出以下错误,
Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'XXXXX'.Cause: java.lang.ClassNotFoundException: Cannot find class: XXXXX
从异常信息来看,明显就是无法从本地检索到alise对应的类,并最终导致sqlSessionFactory等初始化失败。而且吊轨的是,直接在Idea中启动是没有问题的,启动jar包才会出现这个问题
解决方法
参考博主A_Beaver的文章,原来mybatis的facroty需要加载SpringBoot独特的虚拟文件系统,才能识别类路径
public SpringBootVFS() {
this.resourceResolver = new PathMatchingResourcePatternResolver(getClass().getClassLoader());
}
从以上代码看,其实是通过PathMatchingResourcePatternResolver实现资源的加载
修复该问题只需要在mybatis的配置类中,设置一下factory即可,
@Bean(name = "masterSqlSessionFactory")
@Primary
public SqlSessionFactory sqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(dataSource);
bean.setVfs(SpringBootVFS.class);//设置SpringBootVFS
bean.setTypeAliasesPackage("com.fulan.domain.red");
...
}
SpringBoot整合Mybatis及遇到的坑
1. 搭建项目环境
1.1 创建项目
1.2 修改POM文件,添加相关依赖
修改pom.xml文件,在其中添加下面依赖。
<!--Thymeleaf启动器-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--mybatis启动器-->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.3</version>
</dependency>
<!--jdbc启动器-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<!--数据库驱动坐标-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.12</version>
</dependency>
<!--Druid数据源依赖-->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.10</version>
</dependency>
1.3 配置数据源
在application.yml文件中配置如下代码。
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEnconding=utf-8&useSSL=false&serverTimezone=GMT%2B8
username: root
password: root
type: com.alibaba.druid.pool.DruidDataSource
2. 配置Maven的generator插件
2.1 添加generator插件坐标
<!--配置generator插件-->
<plugin>
<groupId>org.mybatis.generator</groupId>
<artifactId>mybatis-generator-maven-plugin</artifactId>
<version>1.4.0</version>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.12</version>
</dependency>
</dependencies>
<!--指定配置文件的路径-->
<configuration>
<configurationFile>${project.basedir}/src/main/resources/generator.xml</configurationFile>
<verbose>true</verbose>
<overwrite>true</overwrite>
</configuration>
</plugin>
2.2 添加generator配置文件
将文件命名为generator.xml,在src/main/resources中添加。
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
"http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
<context id="testTables" targetRuntime="MyBatis3">
<commentGenerator>
<!-- 是否去除自动生成的注释 true:是 : false:否 -->
<property name="suppressAllComments" value="true" />
</commentGenerator>
<!-- 数据库连接信息:驱动类、连接地址、用户名、密码-->
<jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
connectionURL="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEnconding=utf-8&useSSL=false&serverTimezone=UTC"
userId="root" password="root">
</jdbcConnection>
<!-- 默认false,把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer true,把JDBC DECIMAL
和 NUMERIC 类型解析为java.math.BigDecimal -->
<javaTypeResolver>
<property name="forceBigDecimals" value="false" />
</javaTypeResolver>
<!--targetProject:生成PO类的位置-->
<javaModelGenerator targetPackage="com.example.springbootmybatis.pojo"
targetProject=".\src\main\java">
<!--enableSubPackages:是否让schema作为包的后缀-->
<property name="enableSubPackages" value="false" />
<!-- 从数据库返回的值被清理前后的空格 -->
<property name="trimStrings" value="true" />
</javaModelGenerator>
<!--对应的mapper.xml文件 -->
<sqlMapGenerator targetPackage="com.example.springbootmybatis.mapper"
targetProject=".\src\main\java">
<!--enableSubPackages:是否让schema作为包的后缀-->
<property name="enableSubPackages" value="false" />
</sqlMapGenerator>
<!-- 对应的Mapper接口类文件 -->
<javaClientGenerator type="XMLMAPPER"
targetPackage="com.example.springbootmybatis.mapper" targetProject="./src/main/java">
<!--enableSubPackages:是否让schema作为包的后缀-->
<property name="enableSubPackages" value="false" />
</javaClientGenerator>
<!-- 指定数据库表 -->
<table schema="" tableName="users"></table>
<!-- 列出要生成代码的所有表,这里配置的是不生成Example文件 -->
<!-- <table tableName="userinfo" domainObjectName="UserInfoPO" -->
<!-- enableCountByExample="false" enableUpdateByExample="false" -->
<!-- enableDeleteByExample="false" enableSelectByExample="false" -->
<!-- selectByExampleQueryId="false"> -->
<!-- <property name="useActualColumnNames" value="false" /> -->
<!-- </table> -->
</context>
</generatorConfiguration>
2.3 添加generator配置文件的DTD文件
可以在工具栏中的File->Settings中添加,也可以直接在文件中按alt+shift自动添加。
2.4 运行generator插件生成代码
3. 配置资源拷贝插件
3.1 添加资源拷贝插件坐标
<!--配置资源拷贝插件-->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>***.yml</include>
</includes>
</resource>
</resources>
3.2 修改启动类添加@MapperScan注解
package com.example.springbootmybatis;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@MapperScan("com.example.springbootmybatis.mapper")//指定扫描接口与映射配置文件的包名
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
4. 其他配置项
mybatis:
# 扫描classpath中mapper目录下的映射配置文件,针对于映射文件放到了resources目录下
mapper-locations: classpath:/mapper
@Controller
public class PageController {
@RequestMapping("/{page}")
public String showPage(@PathVariable String page){
return page;
}
}
5.2.2 UsersController
package com.example.springbootmybatis.controller;
import com.example.springbootmybatis.pojo.Users;
import com.example.springbootmybatis.service.UsersService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/user")
public class UsersController {
@Autowired
private UsersService usersService;
@PostMapping("/addUser")
public String addUsers(Users users){
try {
this.usersService.addUsers(users);
} catch (Exception e){
e.printStackTrace();
return "error";
}
return "redirect:/ok";
}
}
5.3 创建Service 接口实现类Impl
@Service
public class UsersServiceImpl implements UsersService {
@Autowired
private UsersMapper usersMapper;
@Override
@Transactional
public void addUsers(Users users) {
this.usersMapper.insert(users);
}
}
接口
public interface UsersService {
void addUsers(Users users);
}
遇到的错误
1. Mybatis Generator自动生成,数据库的同名表也会生产的问题
[WARNING] Table Configuration users matched more than one table (test..users,performance_schema..users)
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
在 MyBatis Generator官网 中对这一问题做出了解答。
翻译如下:Mysql 无法正常支持 SQL catalogs 和 schema。因此,最好不要在 generator 配置文件中指定 catalog 以及schema,仅需指定数据表的名字并在 JDBC URL 中指定数据库即可。如果使用 mysql-connector-java 8.x 版本,generator 会为MySql中信息数据库(sys, information_schema, performance_schema)的表生成代码,若要避免这种操作,请在 JDBC URL 中加入属性“nullCatalogMeansCurrent=true”。
修改配置文件generator.xml
<jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
connectionURL="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEnconding=utf-8&useSSL=false&serverTimezone=UTC"
userId="username" password="password">
<property name="nullCatalogMeansCurrent" value="true"/>
</jdbcConnection>
2. 页面出现500错误
2020-06-27 14:23:42.459 ERROR 19676 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Circular view path [addUsers]: would dispatch back to the current handler URL [/addUsers] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)] with root cause
javax.servlet.ServletException: Circular view path [addUsers]: would dispatch back to the current handler URL [/addUsers] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)
at org.springframework.web.servlet.view.InternalResourceView.prepareForRendering(InternalResourceView.java:210) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at
解决方法
查了很多博客,但是都不是自己的问题,自己的问题是在pom.xml配置文件中的资源路径中,没有写所有,而是单独的xml和yml配置文件。要加载所有的静态资源。
<!--原本的-->
<!--资源文件的路径-->
<resource>
<directory>src/main/resources</directory>
<includes>
<include>***.xml</include>
</includes>
<!-- <filtering>false</filtering>-->
</resource>
<!--修改后的-->
<!--资源文件的路径-->
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.*</include>
</includes>
<!-- <filtering>false</filtering>-->
</resource>
以上为个人经验,希望能给大家一个参考,也希望大家多多支持编程网。