org.apache.ibatis.exceptions.PersistenceException

在练习MyBatis的Interceptor时，当执行sqlSession.selectOne总是抛以下异常，看到此异常信息一头蒙，想象不出来哪里会出错，debug调试发现Executor为null，原因是在构建SqlSession时，在Configuration类中，
Executor executor1 = (Executor)this.interceptorChain.pluginAll(executor);得到为null,问题出在实现Inteceptor的插件里，plugin方法没有调用。

// 修改之前
@Override
    public Object plugin(Object o) {
        return null;
    }
// 修改之后
@Override
    public Object plugin(Object o) {
        return Plugin.wrap(o,this);
    }

/**
* 测试
*/
public class AAA {
    public static void main(String[] args) {
        try {
            InputStream rs = Resources.getResourceAsStream("config/mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(rs);
            SqlSession sqlSession = sqlSessionFactory.openSession();
            Map map = new HashMap();
            map.put("id","c0fe6693-6ff9-4845-8d0d-23a6dde205e5");
            SysLogBean o = sqlSession.selectOne("com.company.exer.mapper.SysLogMapper.getById",map);
            System.out.println(o.getOperatorName());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
/**
* MyBatis插件
*/
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class})})
public class PagePlugin implements Interceptor {
    private String sqlId = "";
    public void setSqlId(String sqlId) {
        this.sqlId = sqlId;
    }

    private static class ReflectHelper {
        public static Object getValueByField(Class clasz,Object obj,String fieldStr) {
            Object o = null;
            try {
                if (clasz != null && StringUtils.isNotEmpty(fieldStr)) {
                    Field field = clasz.getDeclaredField(fieldStr);
                    if(field.isAccessible()){
                        o = field.get(obj);
                    }else{
                        field.setAccessible(true);
                        o = field.get(obj);
                        field.setAccessible(false);
                    }
                }
            } catch (NoSuchFieldException e) {
                if(clasz != Object.class){
                    o = getValueByField(clasz.getSuperclass(),obj,fieldStr);
                }else{
                    e.printStackTrace();
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            return o;
        }
    }

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object target = invocation.getTarget();
        if (target instanceof RoutingStatementHandler) {
            PreparedStatementHandler delegate = (PreparedStatementHandler) ReflectHelper.getValueByField(target.getClass(),target, "delegate");
            MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByField(delegate.getClass(), delegate, "mappedStatement");
            if(mappedStatement.getId().matches(sqlId)){
                BoundSql boundSql = delegate.getBoundSql();
                String sql = boundSql.getSql();

            }
        }
        return null;
    }

    @Override
    public Object plugin(Object o) {
        return null;
    }

    @Override
    public void setProperties(Properties properties) {
        this.sqlId = properties.getProperty("sqlId");
    }

    public static void main(String[] args) {

    }
}

异常信息

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.NullPointerException
### Cause: java.lang.NullPointerException
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:107)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:62)
    at com.company.exer.AAA.main(AAA.java:26)
Caused by: java.lang.NullPointerException
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
    ... 3 more