mybatis初始配置及错误说明

1. mybatis使用现在进行了简化，可以直接只引入如下pom就可以了

<dependency>
    <groupid>tk.mybatis</groupid>
    <artifactid>mapper-spring-boot-starter</artifactid>
    <version>1.1.0</version>
</dependency>

2. springboot配置时进行如下配置

启动的application添加注解，如下

@springbootapplication
@mapperscan(basepackages = "com.example.demo.dao")
public class demoapplication {

    public static void main(string[] args) {
        springapplication.run(demoapplication.class, args);
    }
}

启动的application.properties添加配置，如下

mybatis.mapper-locations=classpath:com/example/demo/mapper/xml/*mapper.xml

3. 启动的报错记录说明

如果没有配置这个或者配置错误，@mapperscan(basepackages = "com.example.demo.dao")，会有如下报错，因为没有创建usermapper的实例导致注入失败

description:

field usermapper in com.example.demo.web.usercontroller required a bean of type 'com.example.demo.mapper.usermapper' that could not be found.

the injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.autowired(required=true)

如果application.properties没有正确配置mapper文件的位置，在访问到具体的mapper实现时会有如下报错

org.apache.ibatis.binding.bindingexception: invalid bound statement (not found): com.example.demo.mapper.usermapper.selectbyprimarykey
    at org.apache.ibatis.binding.mappermethod$sqlcommand.<init>(mappermethod.java:214) ~[mybatis-3.4.0.jar:3.4.0]
    at org.apache.ibatis.binding.mappermethod.<init>(mappermethod.java:48) ~[mybatis-3.4.0.jar:3.4.0]
    at org.apache.ibatis.binding.mapperproxy.cachedmappermethod(mapperproxy.java:59) ~[mybatis-3.4.0.jar:3.4.0]
    at org.apache.ibatis.binding.mapperproxy.invoke(mapperproxy.java:52) ~[mybatis-3.4.0.jar:3.4.0]
    at com.sun.proxy.$proxy56.selectbyprimarykey(unknown source) ~[na:na]
    at com.example.demo.web.usercontroller.selectuserbyid(usercontroller.java:23) ~[classes/:na]
    at sun.reflect.nativemethodaccessorimpl.invoke0(native method) ~[na:1.8.0_121]
    at sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.java:62) ~[na:1.8.0_121]
    at sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:43) ~[na:1.8.0_121]
    at java.lang.reflect.method.invoke(method.java:498) ~[na:1.8.0_121]