java.sql.SQLException: "Too many connections"

Question

org.hibernate.exception.JDBCConnectionException: Cannot open connection
OperateDatabase.java queryAll(String hql)查询结果出来啦
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:97)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:161)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1577)
at org.hibernate.loader.Loader.doQuery(Loader.java:696)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
at org.hibernate.loader.Loader.doList(Loader.java:2232)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)
at org.hibernate.loader.Loader.list(Loader.java:2124)
at org.hibernate.loader.custom.CustomLoader.list(CustomLoader.java:312)
at org.hibernate.impl.SessionImpl.listCustomQuery(SessionImpl.java:1723)
at org.hibernate.impl.AbstractSessionImpl.list(AbstractSessionImpl.java:165)
at org.hibernate.impl.SQLQueryImpl.list(SQLQueryImpl.java:175)
at hibernate.OperateDatabase.querySql(OperateDatabase.java:128)
at socket.Server$1.run(Server.java:225)
at java.lang.Thread.run(Unknown Source)
Caused by: java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections"
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1018)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2568)
at com.mysql.jdbc.Connection.(Connection.java:1485)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
... 15 more
Exception in thread "Thread-27" java.lang.NullPointerException
at socket.Server$1.run(Server.java:226)
at java.lang.Thread.run(Unknown Source)
ClientThread.java线程睡眠1000毫秒=1秒
ClientThread.java从客户端发来的聊天内容：{"actiontype":"1","receverName":"192.168.0.107","msgType":false,"senderName":"192.168.0.108","chatDate":"2017-03-03 18:21:08"}
ClientThread.java动作类型1

Exception in thread "Thread-25" org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:97)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:161)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1577)
at org.hibernate.loader.Loader.doQuery(Loader.java:696)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
at org.hibernate.loader.Loader.doList(Loader.java:2232)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)
at org.hibernate.loader.Loader.list(Loader.java:2124)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
at hibernate.OperateDatabase.query(OperateDatabase.java:87)
at chat.ClientThread.run(ClientThread.java:111)
Caused by: java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections"
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1018)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2568)
at com.mysql.jdbc.Connection.(Connection.java:1485)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
... 15 more

hibernate.hbm.xml文件内容，注释部分是连接池，但貌似使用也不管事

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- mysql 数据库驱动 -->
com.mysql.jdbc.Driver
<!-- mysql 数据库名 myandroid 端口3306 -->
jdbc:mysql://localhost:3306/myandroid?useUnicode=true&characterEncoding=utf-8
<!-- 数据的登录用户名 -->
root
<!-- 数据库的登录秘密 -->
admin

      <!-- 下面这一行很重要， 如果hibernate.connection.provider_class没有定义,就会使用内置的连接池，所以如果不想用hibernate内置的连接池，下面这一行必须要写的 -->

    <!-- 方言：为每一种数据库提供适配器，方便转换 -->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

    <!-- 2，其他配置 -->
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>

    <!-- 所有的表映射XML文件必须在此录入  导入映射文件-->
    <mapping resource="hibernate/Customer.hbm.xml"/>
    <mapping resource="hibernate/ChatLog.hbm.xml"/>
    <mapping resource="hibernate/ChatMessage.hbm.xml"/>
    <mapping resource="hibernate/Pitch.hbm.xml"/>
</session-factory>

Answer 1

补充下，实际是两台安卓手机java 安卓客户端在通过台式电脑服务端 tomcat+hibernate +mysql进行聊天通讯 ，两台手机能正常聊一会，但过十几分钟左右服务器就会报错，或许需要用到连接池 但不太会用，望高人指点