IDEA，使用Spring Boot整合MyBatis時出現的問題與解決

問題1: Cannot find class: Xxx

具體描述

運行時，提示找不到某個實體類。
詳細信息如下：

org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'com/chen/org/BookMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Book'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Book

Mapper中的部分代碼如下

    <select id="getAllBooks"  resultType="Book">
		 select  * from book;
	</select>

解決方案

可以嘗試在Mapper中，resultType使用全路徑的類名
如下所示

    <select id="getAllBooks"  resultType="com.chen.org.Book">
		 select  * from book;
	</select>

問題2: 數據庫連接失敗

具體描述

數據庫名、賬戶名、密碼均正確，但就是提示連接失敗。
提示：
The server time zone value ‘�й���׼ʱ��’ is unrecognized or represents more than one time zone
詳細信息如下：

2020-06-11 10:00:22.625 ERROR 6544 --- [reate-484184722] com.alibaba.druid.pool.DruidDataSource   : create connection SQLException, url: jdbc:mysql://127.0.0.1:3306/microprinter?characterEncoding=utf-8, errorCode 0, state 01S00

java.sql.SQLException: 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.
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:73) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:76) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197) ~[mysql-connector-java-8.0.20.jar:8.0.20]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1513) ~[druid-1.1.9.jar:1.1.9]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1578) ~[druid-1.1.9.jar:1.1.9]
	at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2466) ~[druid-1.1.9.jar:1.1.9]

數據庫相關配置如下

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/microprinter?characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource

解決方案

修改數據庫配置中的datasource.url，使用serverTimezone=UTC替代characterEncoding=utf-8

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/microprinter?serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource

問題3: BindingException

具體描述

Mapper，Service相關代碼都編寫正確，但是提示找不到Mapper中的方法
BindingException: Invalid bound statement (not found): com.chen.org.BookMapper.getAllBooks

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.chen.org.BookMapper.getAllBooks

解決方案

首先確保Mapper和Service相關代碼編寫正確，
然後考慮修改pom.xml文件。
在 Maven工程中，運行時會忽略寫在包下的XML文件，因此需要在 pom.xml中重新指明資源文件。

<build>
       ......
 <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
        </resource>
    </resources> 
</build>