将C3P0管理连接重置为其初始状态的建议方法是什么?重置JDBC连接状态(c3p0)
我正在使用Microsoft JDBC驱动程序并在一个连接上设置SET ROWCOUNT 1
。这会导致连接执行的所有查询仅返回一行,即使连接已返回到池并稍后再次获取。我是否应该明确重置值onCheckin
或onCheckout
?
主类
import com.mchange.v2.c3p0.ComboPooledDataSource;
import java.beans.PropertyVetoException;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.ResultSet;
public class Main {
final ComboPooledDataSource cpds;
Main() throws PropertyVetoException {
cpds = new ComboPooledDataSource();
cpds.setDriverClass("com.microsoft.sqlserver.jdbc.SQLServerDriver");
cpds.setJdbcUrl("jdbc:sqlserver://10.42.62.41:1433;databaseName=mach;integratedSecurity=false;SendStringParametersAsUnicode=true;applicationName=panda;");
cpds.setUser("testuser");
cpds.setPassword("welcome123");
cpds.setInitialPoolSize(0);
cpds.setMinPoolSize(1);
cpds.setMaxPoolSize(1);
cpds.setConnectionCustomizerClassName("C3p0ConnectionCustomizer");
cpds.setDescription("Netbeans test project");
}
Connection getConnection() throws SQLException{
return cpds.getConnection();
}
public static void main(String[] args) throws PropertyVetoException, SQLException {
Main m = new Main();
try(Connection connection = m.getConnection()){
Statement stmt = connection.createStatement();
stmt.execute("SET ROWCOUNT 1");
}
try(Connection connection = m.getConnection()){
try(Statement stmt = connection.createStatement()) {
int cnt = 0, rsCnt = 0;
boolean results = stmt.execute("select * from Foo; select * from Bar");
if(results) {
do {
rsCnt++;
ResultSet rs = stmt.getResultSet();
while(rs.next()) {
cnt++;
}
System.out.println(rsCnt + " -> " + cnt);
rs.close();
results = stmt.getMoreResults();
cnt = 0;
} while (results);
}
}
}
}
}
定制 - 主要是看所使用的连接。
import com.mchange.v2.c3p0.AbstractConnectionCustomizer;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
public class C3p0ConnectionCustomizer extends AbstractConnectionCustomizer {
@Override
public void onAcquire(Connection c, String pdsIdt) {
try (Statement stmt = c.createStatement()) {
stmt.execute("SET ROWCOUNT 0");
} catch(SQLException sqle) {
sqle.printStackTrace();
}
}
@Override
public void onCheckOut(Connection c, String pdsIdt) {
System.out.println("Checked out " + c + " [" + pdsIdt + "]");
}
@Override
public void onCheckIn(Connection c, String pdsIdt) throws SQLException {
System.out.println("Checking in " + c + " [" + pdsIdt + "]");
}
}
如果没有SET ROWCOUNT 1
行,上述查询会返回更多行。定制程序日志记录显示正在使用相同的连接。
难道不是更好重置价值onCheckIn而非onCheckOut?我从c3p0文档了解到checkin是异步处理的,而checkout本质上是同步的。 – calvinkrishy
@calvinkrishy - 好点。我已经更新了我的答案。 –