jpa执行mysql报空指针

Posted 2023-05-08

StringBuilder sb = new StringBuilder("SELECT SUM(changedAmount) AS total " +
"FROM HQCreditNoteTmp " +
"WHERE 1=1 " +
"AND TIMESTAMPDIFF(SECOND,createDate,'"+ endDate +"')>0");
if(startDate != null)
sb.append(" AND TIMESTAMPDIFF(SECOND,createDate,'"+ startDate +"')<=0");
else
sb.append(" AND TIMESTAMPDIFF(SECOND,createDate,ADDDATE('"+ endDate +"',-1))<=0");

Query q = entityManager.createQuery(sb.toString(), String.class);　（这句报出空指针）
以上代码是正常的，changedAmount在DB中是varchar类型，统计会不准确，但是将第一句("SELECT SUM(changedAmount) AS total " 改为 "SELECT SUM(CONVERT(changedAmount,DECIMAL(20,7))) AS total "　之后，报出如下空指针
Exception in thread "Thread-37" java.lang.NullPointerException at org.hibernate.dialect.function.StandardAnsiSqlAggregationFunctions$SumFunction.determineJdbcTypeCode(StandardAnsiSqlAggregationFunctions.java:210)
at org.hibernate.dialect.function.StandardAnsiSqlAggregationFunctions$SumFunction.getReturnType(StandardAnsiSqlAggregationFunctions.java:168)
org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:257)
at com.sun.proxy.$Proxy150.createQuery(Unknown Source)
at com.newjetsoft.transaction.repository.jpa.plus.HQAccountDaoPlusImpl.getEODHQCreditAccount(HQAccountDaoPlusImpl.java:40)

单独在数据库中执行sql语句都正确。

在老版本的mysql 3.22中，MySQL的单表限大小为4GB，当时的MySQL的存储引擎还是ISAM存储引擎。但是，当出现MyISAM存储引擎之后，也就是从MySQL 3.23开始，MySQL单表最大限制就已经扩大到了64PB了（官方文档显示）。也就是说，从目前的技术环境来看，MySQL数据库的MyISAM存储 引擎单表大小限制已经不是有MySQL数据库本身来决定，而是由所在主机的OS上面的文件系统来决定了。

　　而MySQL另外一个最流行的存储引擎之一Innodb存储数据的策略是分为两种的，一种是共享表空间存储方式，还有一种是独享表空间存储方式。
　　当使用共享表空间存储方式的时候，Innodb的所有数据保存在一个单独的表空间里面，而这个表空间可以由很多个文件组成，一个表可以跨多个文件存在，所 以其大小限制不再是文件大小的限制，而是其自身的限制。从Innodb的官方文档中可以看到，其表空间的最大限制为64TB，也就是说，Innodb的单 表限制基本上也在64TB左右了，当然这个大小是包括这个表的所有索引等其他相关数据。
　　而当使用独享表空间来存放Innodb的表的时候，每个表的数据以一个单独的文件来存放，这个时候的单表限制，又变成文件系统的大小限制了。 参考技术A 你打印 sb.toString()看看

mysql 8.0 Druid连接时调用getServerCharset报空指针异常解决方法

类似错误信息如下：

16:52:01.163 [Druid-ConnectionPool-Create-1641320886] ERROR com.alibaba.druid.pool.DruidDataSource - create connection error, url: jdbc:mysql://localhost:3306/jf?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.

at sun.reflect.GeneratedConstructorAccessor26.newInstance(Unknown Source) ~[?:?]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_144]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_144]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.Util.getInstance(Util.java:383) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1023) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:997) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:983) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:928) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2576) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2309) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46) ~[mysql-connector-java-5.1.32.jar:?]
at sun.reflect.GeneratedConstructorAccessor23.newInstance(Unknown Source) ~[?:?]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_144]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_144]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:419) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344) ~[mysql-connector-java-5.1.32.jar:?]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1375) ~[druid-1.0.11.jar:1.0.11]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1431) ~[druid-1.0.11.jar:1.0.11]
at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1857) [druid-1.0.11.jar:1.0.11]

Caused by: java.lang.NullPointerException

at com.mysql.jdbc.ConnectionImpl.getServerCharset(ConnectionImpl.java:3299) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1967) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1893) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1287) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2494) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2527) ~[mysql-connector-java-5.1.32.jar:?]
... 12 more

 网上未解决该问题，经排查，使用mysql connector 8版本，问题即解决。所以应该来说是mysql驱动版本的问题。

8.0在驱动器类和连接串上有些变化如下：

jdbc.driverClassName=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/k3c?useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=Hongkong