dao层异常，mapper

Posted 2023-04-11

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参考技术A 截取部分输出

classpath 前加

使用MyBatis Generator自动生成实体mapper和dao层

　　通过MyBatis Generator可以自动生成实体、mapper和dao层，记录一下怎么用的。

主要步骤：　　

　　关于mybatis从数据库反向生成实体、DAO、mapper:
　　参考文章：http://www.cnblogs.com/wangkeai/p/6934683.html
第一种方式：main方法运行（推荐）
　　1.在pom.xml中加入插件依赖：
　　2.写mbgConfiguration.xml文件，jdbc.properties文件
　　3.写/SSM/src/main/java/main/GenMain.java main方法
　　4.运行main函数，刷新

具体步骤：

　　1.在pom.xml中加入插件依赖（需要mybatis的包和反向生成的包）：

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->

<dependency>

    <groupId>org.mybatis</groupId>

    <artifactId>mybatis</artifactId>

    <version>3.4.4</version>

</dependency>

<!-- mybatis-generator-core 反向生成java代码-->

<dependency>

    <groupId>org.mybatis.generator</groupId>

    <artifactId>mybatis-generator-core</artifactId>

    <version>1.3.5</version>

</dependency>

　　2、写mbgConfiguration.xml文件，jdbc.properties文件

　　mbgConfiguration.xml：里面的一些配置也是“因人而异”哦，需要适当修改。文件最后<table></table>就是对数据库中的表作的对应，具体可以看篇头的推荐文章或自己百度。

<?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">    

<!-- 第一种mybatis逆向生成xml配置 -->

<generatorConfiguration> 
   
    <properties resource="jdbc.properties" />  
  
    <context id="sqlserverTables" targetRuntime="MyBatis3">    

        <!-- 生成的pojo，将implements Serializable-->    
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin"></plugin>    

        <commentGenerator>    

            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
    
            <property name="suppressAllComments" value="true" />    

        </commentGenerator>    


    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 数据库链接URL、用户名、密码 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">jdbcConnection </span><span style="color: #ff0000">driverClass</span><span style="color: #0000ff">="${jdbc.driver}"</span><span style="color: #ff0000">    </br>
                    connectionURL</span><span style="color: #0000ff">="${jdbc.url}"</span><span style="color: #ff0000">    </br>
                    userId</span><span style="color: #0000ff">="${jdbc.username}"</span><span style="color: #ff0000">    </br>
                    password</span><span style="color: #0000ff">="${jdbc.password}"</span><span style="color: #0000ff">&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">jdbcConnection</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">      </br>
    默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer    </br>
        true，把JDBC DECIMAL 和 NUMERIC 类型解析为java.math.BigDecimal </br>     
    </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaTypeResolver</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="forceBigDecimals"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="false"</span> <span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaTypeResolver</span><span style="color: #0000ff">&gt;</span> </br></br>   

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">     </br>
    生成model模型，对应的包路径，以及文件存放路径(targetProject)，targetProject可以指定具体的路径,如./src/main/java，    </br>
    也可以使用“MAVEN”来自动生成，这样生成的代码会在target/generatord-source目录下    </br>
    </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #008000">&lt;!--</span><span style="color: #008000">&lt;javaModelGenerator targetPackage="com.joey.mybaties.test.pojo" targetProject="MAVEN"&gt;</span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaModelGenerator </span><span style="color: #ff0000">targetPackage</span><span style="color: #0000ff">="com.yyc.entity"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/java"</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    </br>
        <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 从数据库返回的值被清理前后的空格  </span><span style="color: #008000">--&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="trimStrings"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span> <span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaModelGenerator</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">对应的mapper.xml文件  </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">sqlMapGenerator </span><span style="color: #ff0000">targetPackage</span><span style="color: #0000ff">="mappers"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/resources"</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">sqlMapGenerator</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 对应的Mapper接口类文件 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaClientGenerator </span><span style="color: #ff0000">type</span><span style="color: #0000ff">="XMLMAPPER"</span><span style="color: #ff0000"> targetPackage</span><span style="color: #0000ff">="com.yyc.dao"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/java"</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaClientGenerator</span><span style="color: #0000ff">&gt;</span> </br></br>   


    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 列出要生成代码的所有表，这里配置的是不生成Example文件 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">table </span><span style="color: #ff0000">tableName</span><span style="color: #0000ff">="user_t"</span><span style="color: #ff0000"> domainObjectName</span><span style="color: #0000ff">="UserInfo"</span><span style="color: #ff0000">    </br>
           enableCountByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> enableUpdateByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> enableDeleteByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000">    </br>
           enableSelectByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> selectByExampleQueryId</span><span style="color: #0000ff">="false"</span> <span style="color: #0000ff">&gt;</span>    
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="useActualColumnNames"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="false"</span><span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">table</span><span style="color: #0000ff">&gt;</span>    </br>
<span style="color: #0000ff">&lt;/</span><span style="color: #800000">context</span><span style="color: #0000ff">&gt;</span>    </br>

</generatorConfiguration>

　　由于上面的文件中使用了数据库连接，所以还别忘了数据库的包（相信在准备好学习mybatis前，已经在pom.xml文件中准备好了这些相关依赖）

　　jdbc.properties:　

jdbc.driver=com.mysql.jdbc.Driver

jdbc.url=jdbc:mysql://localhost:3306/ssm?useUnicode=true&characterEncoding=utf8

jdbc.username=root

jdbc.password=123

#定义初始连接数  

initialSize=0  

#定义最大连接数  

maxActive=20  

#定义最大空闲  

maxIdle=20  

#定义最小空闲  

minIdle=1  

#定义最长等待时间  

maxWait=60000

　　3.写GenMain.java main方法

/**
 * 
 */
package main;


import java.io.File;


import java.io.IOException;


import java.sql.SQLException;


import java.util.ArrayList;


import java.util.List;


import org.mybatis.generator.api.MyBatisGenerator;


import org.mybatis.generator.config.Configuration;


import org.mybatis.generator.config.xml.ConfigurationParser;


import org.mybatis.generator.exception.InvalidConfigurationException;


import org.mybatis.generator.exception.XMLParserException;


import org.mybatis.generator.internal.DefaultShellCallback;


/**********************************


@author E-mail:34782655@qq.com

@version 创建时间：2017年6月23日 下午9:18:19

类说明:


mybatis逆向工程main函数</br>



**************************************


/


public class GenMain {


public static void main(String[] args) {  


List<String> warnings = new ArrayList<String>();  


boolean overwrite = true;
　　　　　//如果这里出现空指针，直接写绝对路径即可。


String genCfg = "/mbgConfiguration.xml";  


File configFile = new File(GenMain.class.getResource(genCfg).getFile());  


ConfigurationParser cp = new ConfigurationParser(warnings);  


Configuration config = null;  


try {  


config = cp.parseConfiguration(configFile);  


} catch (IOException e) {  


e.printStackTrace();  


} catch (XMLParserException e) {  


e.printStackTrace();  


}  


DefaultShellCallback callback = new DefaultShellCallback(overwrite);  


MyBatisGenerator myBatisGenerator = null;  


try {  


myBatisGenerator = new MyBatisGenerator(config, callback, warnings); 


} catch (InvalidConfigurationException e) {  


e.printStackTrace();  


}  


try {  


myBatisGenerator.generate(null);  


} catch (SQLException e) {  


e.printStackTrace();  


} catch (IOException e) {  


e.printStackTrace();  


} catch (InterruptedException e) { 


e.printStackTrace();  


}  


}


}

　　4、运行Main方法，刷新项目，就会在上面mbgConfiguration.xml中配置的对应文件的目录下生成实体，mapper,dao了。

第二种方式：maven插件运行

　　1.pom.xml配置插件

　　2.写generatorConfig.xml文件

　　3.运行

具体步骤：　　

　　1.pom.xml配置插件build节点下加入插件：也就是maven一般加入tomcat插件的地方。

<!-- 第二种方式数据库反向生成java -->

<plugin> 

<groupId>org.mybatis.generator</groupId> 

<artifactId>mybatis-generator-maven-plugin</artifactId> 

<version>1.3.2</version> 
<configuration> 

<verbose>true</verbose> 
<overwrite>true</overwrite> 
</configuration> 

</plugin>

　　2.写generatorConfig.xml文件，与mbgConfiguration.xml文件不同的是：文件名固定只能是generatorConfig，文件中要配置数据库连接驱动绝对路径，并且，数据库连接信息url,username,password等都要写固定<classPathEntry location="E:\\MavenRepository\\mysql\\mysql-connector-java\\5.1.38\\mysql-connector-java-5.1.38.jar" />

　　generatorConfig.xml：

<?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">    

<!-- 第二种mybatis逆向生成xml配置 -->    

<generatorConfiguration>  

<!-- 需要指明数据库连接器的绝对路径 -->

    <classPathEntry  

        location="E:\\MavenRepository\\mysql\\mysql-connector-java\\5.1.38\\mysql-connector-java-5.1.38.jar" />     

    <context id="sqlserverTables" targetRuntime="MyBatis3">    

        <!-- 生成的pojo，将implements Serializable-->    

        <plugin type="org.mybatis.generator.plugins.SerializablePlugin"></plugin>    

        <commentGenerator>    

            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->    

            <property name="suppressAllComments" value="true" />    

        </commentGenerator> 

   
    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 数据库链接URL、用户名、密码 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">jdbcConnection </span><span style="color: #ff0000">driverClass</span><span style="color: #0000ff">="com.mysql.jdbc.Driver"</span><span style="color: #ff0000">    </br>
                    connectionURL</span><span style="color: #0000ff">="jdbc:mysql://localhost:3306/ssm"</span><span style="color: #ff0000">    </br>
                    userId</span><span style="color: #0000ff">="root"</span><span style="color: #ff0000">    </br>
                    password</span><span style="color: #0000ff">="123cy-coo.com"</span><span style="color: #0000ff">&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">jdbcConnection</span><span style="color: #0000ff">&gt;</span></br></br>    

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">      </br>
    默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer    </br>
        true，把JDBC DECIMAL 和 NUMERIC 类型解析为java.math.BigDecimal   </br>   
    </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaTypeResolver</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="forceBigDecimals"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="false"</span> <span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaTypeResolver</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">     </br>
    生成model模型，对应的包路径，以及文件存放路径(targetProject)，targetProject可以指定具体的路径,如./src/main/java， </br>   
    也可以使用“MAVEN”来自动生成，这样生成的代码会在target/generatord-source目录下    </br>
    </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #008000">&lt;!--</span><span style="color: #008000">&lt;javaModelGenerator targetPackage="com.joey.mybaties.test.pojo" targetProject="MAVEN"&gt;</span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaModelGenerator </span><span style="color: #ff0000">targetPackage</span><span style="color: #0000ff">="com.yyc.entity"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/java"</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    </br>
        <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 从数据库返回的值被清理前后的空格  </span><span style="color: #008000">--&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="trimStrings"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span> <span style="color: #0000ff">/&gt;</span>  </br>  
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaModelGenerator</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000">对应的mapper.xml文件  </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">sqlMapGenerator </span><span style="color: #ff0000">targetPackage</span><span style="color: #0000ff">="mappers"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/resources"</span><span style="color: #0000ff">&gt;</span>    </br>
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">sqlMapGenerator</span><span style="color: #0000ff">&gt;</span>    </br></br>

    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 对应的Mapper接口类文件 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">javaClientGenerator </span><span style="color: #ff0000">type</span><span style="color: #0000ff">="XMLMAPPER"</span><span style="color: #ff0000"> targetPackage</span><span style="color: #0000ff">="com.yyc.dao"</span><span style="color: #ff0000"> targetProject</span><span style="color: #0000ff">="./src/main/java"</span><span style="color: #0000ff">&gt;</span>    
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="enableSubPackages"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="true"</span><span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">javaClientGenerator</span><span style="color: #0000ff">&gt;</span>    </br></br>


    <span style="color: #008000">&lt;!--</span><span style="color: #008000"> 列出要生成代码的所有表，这里配置的是不生成Example文件 </span><span style="color: #008000">--&gt;</span>    </br>
    <span style="color: #0000ff">&lt;</span><span style="color: #800000">table </span><span style="color: #ff0000">tableName</span><span style="color: #0000ff">="user_t"</span><span style="color: #ff0000"> domainObjectName</span><span style="color: #0000ff">="UserInfo"</span><span style="color: #ff0000">    </br>
           enableCountByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> enableUpdateByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> enableDeleteByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000">    </br>
           enableSelectByExample</span><span style="color: #0000ff">="false"</span><span style="color: #ff0000"> selectByExampleQueryId</span><span style="color: #0000ff">="false"</span> <span style="color: #0000ff">&gt;</span>    
        <span style="color: #0000ff">&lt;</span><span style="color: #800000">property </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="useActualColumnNames"</span><span style="color: #ff0000"> value</span><span style="color: #0000ff">="false"</span><span style="color: #0000ff">/&gt;</span>    </br>
    <span style="color: #0000ff">&lt;/</span><span style="color: #800000">table</span><span style="color: #0000ff">&gt;</span></br>    
<span style="color: #0000ff">&lt;/</span><span style="color: #800000">context</span><span style="color: #0000ff">&gt;</span> </br>   

</generatorConfiguration>

　　 3.运行方法：在eclipse 中，选择pom.xml文件，击右键先择Run AS——>Maven Build… ——>在Goals框中输入：mybatis-generator:generate 运行即可。

因为第一种xml文件的配置比较灵活，不像第二种xml中还需要写死数据库驱动地址和连接信息，并且还要多加一个jar插件。所以推荐第一种方式

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