[ ExecutorException ] org.apache.ibatis.executor.ExecutorException:No constructor found in XXX match

Mybatis中第一次遇到这个问题，做个笔记!

No constructor found in com.mybatis.bean.Mybean$InnerBean matching [java.lang.String, java.lang.String]

### Cause: org.apache.ibatis.executor.ExecutorException: No constructor found in com.mybatis.bean.Mybean$InnerBeanmatching [java.lang.String, java.lang.String]
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at com.mybatis.test4.Test4.main(Test4.java:15)
Caused by: org.apache.ibatis.executor.ExecutorException: No constructor found in com.mybatis.bean.Mybean$InnerBean matching [java.lang.String, java.lang.String]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createByConstructorSignature(DefaultResultSetHandler.java:656)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:605)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:578)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:383)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:342)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:317)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:290)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:187)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)

查找了很多资料，大部分结果可以分为两种：

一、实体类中没有使用内部类

这种情况下，其实就是重写了构造器后，忘了补写一个默认的构造器了。此类的错误还经常出现在spring等这种大量使用反射的框架中。因为这些框架在调用反射的类后会默认调用默认的构造器。

二、使用内部类，Mybatis.xml中返回类型为内部类

1. 记录一下内部类在xml中写法

   <select id="selectAll" resultType="com.mybatis.bean.Mybean$InnerBean">
   	select id, name from user 
   </select>
   

使用“$”去分割内部类与外部类，而不是“.”
2. 此时如果出现此异常
Collection标签使用内部类，该内部类必须为静态内部类

非静态内部类依赖外部类实例，所以报错No constructor found in matching [java.lang.Long, java.lang.String，关于内部类反射可以参考http://blog.csdn.net/ldstartnow/article/details/52782420，不过并不是必须要显式构造函数

public class Mybean {
    private String age;
    private String old;
  
    // 添加该内部类为静态内部类， 否则反射会出现异常
    public static class Bean{
        private String id;
        private String name;
    }