MySQL、c3p0和Apache Felix集成

Question

我将MySQL集成到Apache Felix中。首先，我使用bndtools生成MySQL捆绑包和c3p0捆绑包。然后将它们全部添加到Apache Felix环境中。我为连接池创建了一个类，如下所示：

    public final class C3P0Manager {

        private static C3P0Manager instance;
        private DataSource pooled;

        private C3P0Manager() {
            // Of course, it is better to put all properties into a configuration file.
            // I just list them here for easy reading.

            ComboPooledDataSource cpds = new ComboPooledDataSource();
            cpds.setDriverClass("com.mysql.jdbc.Driver"));
            cpds.setJdbcUrl("jdbc:mysql://localhost/my-database?autoReconnect=true&characterSetResults=UTF-8&characterEncoding=UTF-8&useUnicode=yes");
            cpds.setUser("user");
            cpds.setPassword("password");
            cpds.setInitialPoolSize(3);
            cpds.setMaxPoolSize(15);
            cpds.setMaxIdleTime(1800);
            cpds.setAutoCommitOnClose(true);
            pooled(cpds);
        }

        public static C3P0Manager instance() throws Exception {
            if (instance == null) {
                instance = new C3P0Manager();
            }
            return instance;
        }

        public DataSource getPooled() throws SQLException {
            return pooled;
        }
    }

如果我运行JUnit测试，它工作得很好。但在Apache Felix包上运行时失败,并出现异常消息。Activator类中的用法：

    Class.forName("com.mysql.jdbc.Driver");
    DataSource pooled = C3P0Manager.instance().getPooled();
    Connection con = pooled.getConnection();
    PreparedStatement stmt = null;
    ResultSet rs = null;
    int total;

    try {
        stmt = con.prepareStatement("SELECT count(*) FROM users", Statement.NO_GENERATED_KEYS);
        rs = stmt.executeQuery();
        if (rs.next()) {
            total = rs.getInt(1);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            stmt.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
    System.out.println("total = " + total);

错误消息：

    java.sql.SQLException: Connections could not be acquired from the underlying database!
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
    ...
    Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
    ...

如果我只使用（不使用c3p0)，MySQL可以工作：

    Class.forName("com.mysql.jdbc.Driver");
    Connection con = DriverManager.getConnection("jdbc:mysql://localhost/my-database?autoReconnect=true&characterSetResults=UTF-8&characterEncoding=UTF-8&useUnicode=yes","user","password");
    Statement statement = connect.createStatement();
    ResultSet resultSet = statement.executeQuery("SELECT count(*) FROM users");

所以我认为问题是由于C3P0。请帮帮我.多谢了。

Answer 1

我懒得修改c3p0源代码并重新构建新的c3p0包版本：）。所以我尝试Apache DBCP包：

org.apache.servicemix.bundles.commons-pool-1.5.4
org.apache.servicemix.bundles.commons-dbcp-1.4.0
(dbcp needs pool to work)

对MySQL数据库进行CRUD是可以的。

如果有人想要使用这些包，这里有：

http://mvnrepository.com/artifact/org.apache.servicemix.bundles/org.apache.servicemix.bundles.commons-pool
http://mvnrepository.com/artifact/org.apache.servicemix.bundles/org.apache.servicemix.bundles.commons-dbcp

当我有时间的时候，如果有人已经为它构建了一个bundle，我会看一看bonecp。或修改c3p0以使用它。