警告: Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class java.util.HashMap
六月 22, 2018 10:33:24 上午 org.apache.catalina.core.StandardContext reload
Error creating bean with name 'userController': Unsatisfied dependency expressed through field 'userService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userServiceImpl': Unsatisfied dependency expressed through field 'userDao'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userDaoImpl': Unsatisfied dependency expressed through field 'baseDao'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'baseDao' defined in file [D:\E\workspace\eclipse\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\mavenDemo\WEB-INF\classes\com\sts\dao\BaseDao.class]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required
-- 从上面的问题描述可以看到，在创建baseDao时报错，继续往后看可以看到sqlSessionFactory' or 'sqlSessionTemplate获取失败，在构建baseDao的时候，继承了SqlSessionDaoSupport。在baseDao的方法中调用sqlSessionFactory来执行sql语句，而调用的sqlSessionFactory未实例化导致异常。
为什么会出现这种现象？原来在mybatis-spring-1.2.0之后的版本中取消了自动注入SqlSessionFactory 和 SqlSessionTemplate，需要手动添加：
只需要在BaseDao中加入下面的代码即可：
@Autowired
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory){
super.setSqlSessionFactory(sqlSessionFactory);
}
二、Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+,
5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance
with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly
disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
上述问题的原因是：MySQL在高版本需要指明是否进行SSL连接，在jdbc.url后加上useSSL=true即可
三、org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain
JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create
PoolableConnectionFactory (Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the
server.)
### The error may exist in file [D:\E\workspace\eclipse\.metadata\.plugins\org.eclipse.wst.server.core
\tmp0\wtpwebapps\mavenDemo\WEB-INF\classes\com\sts\dao\common\user.mapper.xml]
### The error may involve user.login### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection;
nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory
(Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the
server.)
从上面的描述可以看出，数据库连接失败，所以仔细检查下数据库的url连接。
例：
jdbc:mysql://${database.ip}:3306/${database.name}?zeroDateTimeBehavior=convertToNull&useUnicode=true&
characterEncoding=utf8