我正在使用 Tomcat 构建一个 Web 项目，我必须从 MySQL 数据库中获取一些日期，为此我使用 HikariCP。 不幸的是，在多次获取之后，我得到了 SQLTransientConnectionException。
13:34:33.915 [http-nio-8081-exec-14] ERROR de.intranet.data.db.DBAccess - SQL error in getLatestModification for category hausnachrichten: Cannot invoke "java.sql.Connection.prepareStatement(String)" because the return value of "de.intranet.data.db.DBAccess.getConnection()" is null
13:34:33.915 [http-nio-8081-exec-14] DEBUG de.intranet.data.db.DBAccess - Existing getLatestModification for category hausnachrichten: null
13:34:38.957 [http-nio-8081-exec-13] ERROR de.intranet.data.db.DBConnection - Failed to retrieve a connection from the connection pool.
java.sql.SQLTransientConnectionException: HikariPool-2 - Connection is not available, request timed out after 30010ms.
at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:696) ~[HikariCP-5.0.1.jar:?]
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:181) ~[HikariCP-5.0.1.jar:?]
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:146) ~[HikariCP-5.0.1.jar:?]
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:100) ~[HikariCP-5.0.1.jar:?]
at de.intranet.data.db.DBConnection.getConnection(DBConnection.java:131) [classes/:?]
at de.intranet.data.db.DBAccess.getLatestModification(DBAccess.java:735) [classes/:?]
at de.intranet.http.ServletDashboardPrepopulate.doPost(ServletDashboardPrepopulate.java:80) [classes/:?]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590) [servlet-api.jar:6.0]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) [servlet-api.jar:6.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) [catalina.jar:10.1.10]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) [catalina.jar:10.1.10]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) [tomcat-websocket.jar:10.1.10]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) [catalina.jar:10.1.10]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) [catalina.jar:10.1.10]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:166) [catalina.jar:10.1.10]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) [catalina.jar:10.1.10]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) [catalina.jar:10.1.10]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) [catalina.jar:10.1.10]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) [catalina.jar:10.1.10]
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:676) [catalina.jar:10.1.10]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [catalina.jar:10.1.10]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:341) [catalina.jar:10.1.10]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) [tomcat-coyote.jar:10.1.10]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) [tomcat-coyote.jar:10.1.10]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:894) [tomcat-coyote.jar:10.1.10]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741) [tomcat-coyote.jar:10.1.10]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) [tomcat-coyote.jar:10.1.10]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-util.jar:10.1.10]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-util.jar:10.1.10]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-util.jar:10.1.10]
at java.base/java.lang.Thread.run(Thread.java:1589) [?:?]
对我来说，就我正在使用的
try-with-statements13:33:28.868 [http-nio-8081-exec-11] DEBUG de.intranet.http.ServletDashboardPrepopulate - Connection Pool Stats - Active: 10, Idle: null
13:33:33.903 [http-nio-8081-exec-14] DEBUG de.intranet.http.ServletDashboardPrepopulate - Connection Pool Stats - Active: 10, Idle: null
13:33:38.934 [http-nio-8081-exec-13] DEBUG de.intranet.http.ServletDashboardPrepopulate - Connection Pool Stats - Active: 10, Idle: null
13:33:43.960 [http-nio-8081-exec-2] DEBUG de.intranet.http.ServletDashboardPrepopulate - Connection Pool Stats - Active: 10, Idle: null
13:33:48.995 [http-nio-8081-exec-16] DEBUG de.intranet.http.ServletDashboardPrepopulate - Connection Pool Stats - Active: 10, Idle: null
13:33:53.856 [http-nio-8081-exec-9] ERROR de.intranet.data.db.DBConnection - Failed to retrieve a connection from the connection pool.
java.sql.SQLTransientConnectionException: HikariPool-2 - Connection is not available, request timed out after 30001ms.
at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:696) ~[HikariCP-5.0.1.jar:?]
(rest is same as above)
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
// Initialize a map to store category names and their corresponding latest
// modification dates
Map<String, String> dateMap = new HashMap<>();
// Retrieve the ServletContext and DBAccess instance from the request
ServletContext servletContext = request.getServletContext();
DBAccess dbAccess = (DBAccess) servletContext.getAttribute("dbConnection");
// Define a date format for formatting the modification dates in the response
SimpleDateFormat sdf = new SimpleDateFormat("dd.MM.yyyy");
try {
Map<String, Integer> poolStats = dbAccess.getConnectionPoolStats();
logger.debug("Connection Pool Stats - Active: {}, Idle: {}", poolStats.get("active"),
poolStats.get("idle"));
} catch (Exception e) {
logger.error("Error retrieving connection pool stats: {}", e.getMessage());
}
// Iterate through each file category and retrieve the latest modification date
for (DBFilesTableCategory category : DBFilesTableCategory.values()) {
Date lastDate = dbAccess.getLatestModification(category);
// If a modification date is available, add it to the dateMap
if (lastDate != null) {
dateMap.put(category.name(), sdf.format(lastDate));
} else {
dateMap.put(category.name(), "Keine Dateien vorhanden");
}
}
// Convert the dateMap to a JSON response using Gson
Gson gson = new Gson();
String jsonResponse = gson.toJson(dateMap);
// Write the JSON response to the HttpServletResponse
response.getWriter().write(jsonResponse);
} catch (Exception e) {
// Log any exceptions that occur during the processing of the request
logger.error("Error while prepopulating dashboard: {}", e.getMessage());
// Send an internal server error response to the client
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
}
}
public class DBAccess extends DBConnection {
public Date getLatestModification(DBFilesTableCategory category) {
// Variable to store the latest modification date
Date latestDate = null;
// Convert the category enum to a string
String categoryString = category.toString();
// SQL query to retrieve the maximum upload date for files in the specified
// category
String query = "SELECT MAX(f_uploadDate) AS latestDate FROM files WHERE f_category = ?";
try (Connection connection = this.getConnection();
PreparedStatement preparedStatement = this.getConnection().prepareStatement(query)) {
// Set the category as a parameter in the prepared statement
preparedStatement.setString(1, categoryString);
logger.debug("Executing query: {}", preparedStatement);
// Execute the query and retrieve the result set
try (ResultSet resultSet = preparedStatement.executeQuery()) {
// If a row is returned, retrieve the latest date
if (resultSet.next()) {
latestDate = resultSet.getDate("latestDate");
}
} catch (SQLException e) {
// Handle any SQL exceptions by printing the stack trace
logger.error("SQL error in getLatestModification for category {}: {}", categoryString, e.getMessage());
}
} catch (Exception e) {
// Handle any SQL exceptions by printing the stack trace
logger.error("SQL error in getLatestModification for category {}: {}", categoryString, e.getMessage());
}
logger.debug("Existing getLatestModification for category {}: {}", categoryString, latestDate);
// Return the latest modification date, or null if no files are found
return latestDate;
}
}
也许我在实例初始化时如何启动连接有问题？
public class DBConnection {
// The HikariConfig object for configuring the connection pool
private HikariConfig config;
private HikariDataSource dataSource;
// Static initializer for loading the MySQL JDBC driver
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
throw new RuntimeException("MySQL JDBC driver not found", e);
}
}
public DBConnection(String url, String username, String password) {
// Create a new DBAccess instance with the specified database connection details
config = new HikariConfig();
// Set the URL, username, and password for the database connection
config.setJdbcUrl(url);
config.setUsername(username);
config.setPassword(password);
config.addDataSourceProperty("cachePrepStmts", "true");
config.addDataSourceProperty("prepStmtCacheSize", "250");
config.addDataSourceProperty("prepStmtCacheSqlLimit", "2048");
dataSource = new HikariDataSource(config);
}
}
@WebListener
public class WebServletContextListener implements ServletContextListener {
// Attribute name for the database connection
private static final String DB_CONNECTION_ATTR = "dbConnection";
@Override
public void contextInitialized(ServletContextEvent event) {
// Pass the servlet context to ConfigUtil
ConfigUtil.setServletContext(event.getServletContext());
// Create a new DBAccess instance with the specified database connection details
DBAccess dbConnection = new DBAccess(ConfigUtil.getDatabaseUrl(), ConfigUtil.getDatabaseUsername(),
ConfigUtil.getDatabasePassword());
// Set the DBAccess instance as a servlet context attribute
event.getServletContext().setAttribute(DB_CONNECTION_ATTR, dbConnection);
}
数据库的日志完全是空的，我不知道我能做什么。
也许你们中的一些人知道如何隔离错误，甚至以前遇到过类似的问题并有解决方案。
问候
感谢Thomas Kläger的回复。 这为我解决了这个问题：
try (Connection connection = this.getConnection();
PreparedStatement preparedStatement = connection.prepareStatement(query))
而不是
try (Connection connection = this.getConnection();
PreparedStatement preparedStatement = this.getConnection().prepareStatement(query))
您在这里泄漏连接：
try (Connection connection = this.getConnection();
PreparedStatement preparedStatement = this.getConnection().prepareStatement(query)) {
此片段打开两个连接，但只有一个被声明为要关闭的资源。第二个资源是在第二个连接上创建的
PreparedStatement解决方案是只打开一个连接并使用该连接来调用
prepareStatement() try (Connection connection = this.getConnection();
PreparedStatement preparedStatement = connection.prepareStatement(query)) {