Java.sql.connection对象第二次不工作
Java.sql.connection对象第二次不工作
提问于 2015-06-26 13:53:01
我在我的程序中为jboss应用服务器声明了Resource注解。我正在使用这些注释创建连接对象。当我第一次使用connection时，它会建立连接，并且通过使用java.sql.ResultSetMetaData，我能够获得值。但在第二次遇到异常时，我发现"java.sql.SQLException: Connection is not associated with a managed connection.org.jboss.jca.adapters.jdbc.jdk6.WrappedConnectionJDK6@19adb".为什么我会得到这个异常。
我给我的jboss standalone.xml文件和我的java程序如下
standalone.xml：
<datasources>
<datasource jndi-name="java:jboss/datasources/dcimpl" pool-name="dcimpl_pool" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/dcimpl?zeroDateTimeBehavior=convertToNull
</connection-url>
<driver>
mysqldriver
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
50
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
</password>
</security>
<validation>
<validate-on-match>
false
</validate-on-match>
<background-validation>
false
</background-validation>
<useFastFail>
false
</useFastFail>
</validation>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
<datasource jndi-name="java:jboss/datasources/dcframework" pool-name="dcframework_pool" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/dcframework?zeroDateTimeBehavior=convertToNull
</connection-url>
<driver>
mysqldriver
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
50
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
</password>
</security>
<validation>
<validate-on-match>
false
</validate-on-match>
<background-validation>
false
</background-validation>
<useFastFail>
false
</useFastFail>
</validation>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
<datasource jndi-name="java:jboss/datasources/dctest1" pool-name="dcframework_pool" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/dc_testing1?zeroDateTimeBehavior=convertToNull
</connection-url>
<driver>
mysqldriver
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
50
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
</password>
</security>
<validation>
<validate-on-match>
false
</validate-on-match>
<background-validation>
false
</background-validation>
<useFastFail>
false
</useFastFail>
</validation>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
<datasource jndi-name="java:jboss/datasources/dctest2" pool-name="dcframework_pool" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/dc_testing2?zeroDateTimeBehavior=convertToNull
</connection-url>
<driver>
mysqldriver
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
50
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
</password>
</security>
<validation>
<validate-on-match>
false
</validate-on-match>
<background-validation>
false
</background-validation>
<useFastFail>
false
</useFastFail>
</validation>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
<datasource jndi-name="java:jboss/datasources/dctest3" pool-name="dcframework_pool" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/dc_testing3?zeroDateTimeBehavior=convertToNull
</connection-url>
<driver>
mysqldriver
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
50
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
</password>
</security>
<validation>
<validate-on-match>
false
</validate-on-match>
<background-validation>
false
</background-validation>
<useFastFail>
false
</useFastFail>
</validation>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
<drivers>
<driver name="h2" module="com.h2database.h2">
<xa-datasource-class>
org.h2.jdbcx.JdbcDataSource
</xa-datasource-class>
</driver>
<driver name="postgresql" module="org.postgresql">
<xa-datasource-class>
org.postgresql.xa.PGXADataSource
</xa-datasource-class>
</driver>
<driver name="mysqldriver" module="com.mysql"/>
</drivers>
</datasources>我的java程序：
@Stateless
public class DispalyConfigScreenBO {
HashMap<String, Connection> memoryConn = new HashMap<String, Connection>();
@Resource(mappedName = "java:jboss/datasources/dctest1")
DataSource dataSource1;
@Resource(mappedName = "java:jboss/datasources/dctest2")
DataSource dataSource2;
@Resource(mappedName = "java:jboss/datasources/dctest3")
DataSource dataSource3;
public String createPoolConns() {
try {
Connection con1 = dataSource1.getConnection();
memoryConn.put("dctest1", con1);
Connection con2 = dataSource2.getConnection();
memoryConn.put("dctest2", con2);
Connection con3 = dataSource3.getConnection();
memoryConn.put("dctest3", con3);
} catch (Exception e) {
System.out.println("Exception in createPoolConns = " + e);
}
return "success";
}
public String parseColumnnames(String value, String datasource)
throws Exception {
StringBuilder output = new StringBuilder();
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = memoryConn.get(datasource);
if (conn == null) {
return null;
} else {
st = conn.createStatement();
rs = st.executeQuery((value + " LIMIT 1").replace(";", ""));
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i <= numberOfColumns; i++) {
if (i == numberOfColumns) {
output.append(rsMetaData.getColumnLabel(i));
} else {
output.append(rsMetaData.getColumnLabel(i));
output.append(",");
}
}
}
} catch (Exception dbException) {
dbException.printStackTrace();
} finally {
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (conn != null) {
conn.close();
}
}
return output.toString();
}我正在创建hashmap，并将所有连接对象放在该hashmap中，并在任何需要获取连接对象的地方使用该hashmap。但除非是第一次，否则不能工作。
帮帮我。
回答 1
Stack Overflow用户
发布于 2015-06-26 13:57:03
您在parseColumnnames的末尾关闭了连接-所以当您稍后尝试使用它时，它将不起作用……您不能使用关闭的连接。
我建议你不要尝试像这样缓存连接。取而代之的是，依靠数据源实现来适当地汇集连接，并在每次需要连接时调用getConnection()。(我还建议使用try-with-resources来关闭所有内容，而不是全部手动完成。)
这样的话：
- 您将克服当前的问题
- 您无需担心同时处理尝试使用同一连接的多个线程
- 您的代码中有一个清晰的连接生命周期，将“我们如何使其高效”这句话抛给连接池，而连接池存在的唯一原因就是做好这项工作
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/31065861
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