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我编写了一个简单的 Java 代码，它尝试将文件存储在 hsqldb 数据库中。它所做的只是从某个目录读取文件并将它们放入数据库中。它是单线程的，但我使用来自 apache commons.dbcp 的池连接，以便以后能够处理多线程访问。

问题是读取几个文件后代码块。

请在下面找到整个源代码。

程序.java

import java.io.File;
import java.io.IOException;
import java.sql.SQLException;

import javax.sql.DataSource;

import org.apache.commons.dbcp.ConnectionFactory;
import org.apache.commons.dbcp.DriverManagerConnectionFactory;
import org.apache.commons.dbcp.PoolableConnectionFactory;
import org.apache.commons.dbcp.PoolingDataSource;
import org.apache.commons.pool.KeyedObjectPoolFactory;
import org.apache.commons.pool.impl.GenericKeyedObjectPoolFactory;
import org.apache.commons.pool.impl.GenericObjectPool;

public class Program {
  public static DataSource getPoolingDataSource(String driverClass, String url, String user, String password) throws ClassNotFoundException {
    Class.forName(driverClass);
    ConnectionFactory connectionFactory = new DriverManagerConnectionFactory(url, user, password);
    GenericObjectPool connectionPool = new GenericObjectPool();
    KeyedObjectPoolFactory stmtPool = new GenericKeyedObjectPoolFactory(null);
    new PoolableConnectionFactory(connectionFactory, connectionPool, stmtPool, null, false, true);
    return new PoolingDataSource(connectionPool);
  }

  public static void main(String[] args) throws ClassNotFoundException, SQLException, IOException, InterruptedException {
    String root = args.length == 0 ? "c:/Work/java/ntxdb" : args[0];

    Runtime run = Runtime.getRuntime();
    Process pr = run.exec("cmd /c del /s/q c:\\tmp\\file.db*");
    pr.waitFor();
    DataSource ds = getPoolingDataSource("org.hsqldb.jdbcDriver", "jdbc:hsqldb:file:c:/tmp/file.db", "sa", "");
    HsqldbFileStorage fs = new HsqldbFileStorage(ds);
    putFiles(fs, new File(root));
  }

  private static void putFiles(HsqldbFileStorage fs, File parent) throws IOException, SQLException {
    for (File child : parent.listFiles()) {
      if (child.isDirectory()) {
        putFiles(fs, child);
      } else {
        System.out.println(child.getCanonicalPath());
        fs.put(child);
      }
    }
  }
}

HsqldbFileStorage.java

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.sql.DataSource;

public class HsqldbFileStorage {
  private static final String SET_SQL = "MERGE INTO test" +
    "  USING (VALUES ?, CAST(? AS BLOB)) I (name, data)" +
    "  ON (test.name=I.name)" +
    "  WHEN MATCHED THEN UPDATE SET test.data = I.data" +
    "  WHEN NOT MATCHED THEN INSERT (name, data) VALUES (I.name, I.data)";
  private DataSource m_dataSource;

  public HsqldbFileStorage(DataSource dataSource) throws SQLException {
    super();
    m_dataSource = dataSource;
    Connection c = dataSource.getConnection();
    c.createStatement().execute("Create Cached Table IF NOT EXISTS test (name VARCHAR(256), data BLOB(10M));");
  }

  public void put(File file) throws IOException, SQLException {
    put(file.getCanonicalPath(), file);
  }

  public void put(String name, File file) throws IOException, SQLException {
    InputStream is = new BufferedInputStream(new FileInputStream(file));
    try {
      put(name, is);
    } finally {
      is.close();
    }
  }

  public void put(String name, InputStream data) throws SQLException, IOException {
    PreparedStatement set = m_dataSource.getConnection().prepareStatement(SET_SQL);
    try {
      set.setString(1, name);
      set.setBinaryStream(2, data);
      set.executeUpdate();
    } finally {
      set.close();
    }
  }
}

代码依赖于 commons-dbcp 1.4、commons-pool 1.6 和 hsqldb 2.2.9

在项目目录本身上运行它应该在数据库中放置 62 个文件（我那里的文件比前面提到的两个源文件多得多），为每个文件打印一行。

不幸的是，它阻塞了第八个文件，并带有以下堆栈跟踪：

  at java.lang.Object.wait(Object.java:-1)
  at java.lang.Object.wait(Object.java:485)
  at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1118)
  at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
  at HsqldbFileStorage.put(HsqldbFileStorage.java:41)
  at HsqldbFileStorage.put(HsqldbFileStorage.java:34)
  at HsqldbFileStorage.put(HsqldbFileStorage.java:28)
  at Program.putFiles(Program.java:42)
  at Program.putFiles(Program.java:39)
  at Program.putFiles(Program.java:39)
  at Program.main(Program.java:33)

我究竟做错了什么？

4

1 回答 1

3

您正在调用：

m_dataSource.getConnection()

在您的 put(String, InputStream) 方法中。这会创建一个您永远不会关闭的新连接。

因此，当您在某个阶段将 62 个文件放入其中时，它将达到池中的最大连接数，之后池将等待连接返回到池中。

如果您这样修改您的方法：

  public void put(String name, InputStream data) throws SQLException, IOException {
    Connection con = null;
    PreparedStatement set = null;
    try {
      con = m_dataSource.getConnection();
      set.prepareStatement(SET_SQL);
      set.setString(1, name);
      set.setBinaryStream(2, data);
      set.executeUpdate();
    } finally {
      if (set != null) {
        set.close();
      }
      if (con != null) {
        con.close();
      }
    }
  }

请注意，当您通过池访问连接时，您仍然需要调用 close。这实际上不会关闭连接，而是将其返回到池中。

于 2013-03-02T14:32:58.790 回答