I'm all new in couchbase, I copy/paste the first code example in (http://www.couchbase.com/communities/java/getting-started) in my Eclipse project but when I run it and check back the server i can't find the document, below is console output:
2014-03-16 17:30:42.390 INFO com.couchbase.client.CouchbaseConnection: Added {QA sa=/127.0.0.1:11210, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
2014-03-16 17:30:42.390 INFO com.couchbase.client.CouchbaseClient: CouchbaseConnectionFactory{, bucket='trust', nodes=[http://localhost:8091/pools], order=RANDOM, opTimeout=2500, opQueue=16384, opQueueBlockTime=10000, obsPollInt=10, obsPollMax=500, obsTimeout=5000, viewConns=10, viewTimeout=75000, viewWorkers=1, configCheck=10, reconnectInt=1100, failureMode=Redistribute, hashAlgo=NATIVE_HASH}
2014-03-16 17:30:42.390 INFO com.couchbase.client.CouchbaseConnection: Connection state changed for sun.nio.ch.SelectionKeyImpl#f8ae79
2014-03-16 17:30:42.468 INFO com.couchbase.client.CouchbaseClient: viewmode property isn't defined. Setting viewmode to production mode
2014-03-16 17:30:42.703 INFO net.spy.memcached.auth.AuthThread: Authenticated to localhost/127.0.0.1:11210
and here is my java class:
public class Test_ {
public static void main(String[] args) throws Exception {
// (Subset) of nodes in the cluster to establish a connection
List hosts = Arrays.asList(new URI("http://localhost:8091/pools"));
// Name of the Bucket to connect to
String bucket = "trust";
// Password of the bucket (empty) string if none
String password = "HIDDEN";
// Connect to the Cluster
CouchbaseClient client = new CouchbaseClient(hosts, bucket, password);
// Store a Document
client.set("33", "test my java code").get();
// Retreive the Document and print it
//System.out.println(client.get("33"));
// Shutting down properly
client.shutdown();
}
}
Solved, it was just the firewall blocking the port 11210.
Related
I am using docker-java API to execute docker API in my project. I didn't find any suitable method which lists down docker CPU memory usage as
GET /v1.24/containers/redis1/stats HTTP/1.1 with the help of docker-java API
Dependency
compile group: 'com.github.docker-java', name: 'docker-java', version: '3.1.2'
Code
public static void execute() {
DockerClient dockerClient = DockerClientBuilder.getInstance().build();
dockerClient.statsCmd("containerName");
}
I didn't get any output
Tell me how to execute docker stats with docker-java api
This works for me
public Statistics getNextStatistics() throws ProfilingException {
AsyncResultCallback<Statistics> callback = new AsyncResultCallback<>();
client.statsCmd(containerId).exec(callback);
Statistics stats;
try {
stats = callback.awaitResult();
callback.close();
} catch (RuntimeException | IOException e) {
// you may want to throw an exception here
}
return stats; // this may be null or invalid if the container has terminated
}
DockerClient is where we can establish a connection between a Docker engine/daemon and our application.
By default, the Docker daemon can only be accessible at the unix:///var/run/docker.sock file. We can locally communicate with the Docker engine listening on the Unix socket unless otherwise configured.
we can open a connection in two steps:
DefaultDockerClientConfig.Builder config
= DefaultDockerClientConfig.createDefaultConfigBuilder();
DockerClient dockerClient = DockerClientBuilder
.getInstance(config)
.build();
Since engines could rely on other characteristics, the client is also configurable with different conditions.
For example, the builder accepts a server URL, that is, we can update the connection value if the engine is available on port 2375:
DockerClient dockerClient
= DockerClientBuilder.getInstance("tcp://docker.baeldung.com:2375").build();
Note that we need to prepend the connection string with unix:// or tcp:// depending on the connection type.
How do you connect to a MySQL database in Java?
When I try, I get
java.sql.SQLException: No suitable driver found for jdbc:mysql://database/table
at java.sql.DriverManager.getConnection(DriverManager.java:689)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
Or
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
Or
java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
Here's a step by step explanation how to install MySQL and JDBC and how to use it:
Download and install the MySQL server. Just do it the usual way. Remember the port number whenever you've changed it. It's by default 3306.
Download the JDBC driver and put in classpath, extract the ZIP file and put the containing JAR file in the classpath. The vendor-specific JDBC driver is a concrete implementation of the JDBC API (tutorial here).
If you're using an IDE like Eclipse or Netbeans, then you can add it to the classpath by adding the JAR file as Library to the Build Path in project's properties.
If you're doing it "plain vanilla" in the command console, then you need to specify the path to the JAR file in the -cp or -classpath argument when executing your Java application.
java -cp .;/path/to/mysql-connector.jar com.example.YourClass
The . is just there to add the current directory to the classpath as well so that it can locate com.example.YourClass and the ; is the classpath separator as it is in Windows. In Unix and clones : should be used.
Create a database in MySQL. Let's create a database javabase. You of course want World Domination, so let's use UTF-8 as well.
CREATE DATABASE javabase DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci;
Create a user for Java and grant it access. Simply because using root is a bad practice.
CREATE USER 'java'#'localhost' IDENTIFIED BY 'password';
GRANT ALL ON javabase.* TO 'java'#'localhost' IDENTIFIED BY 'password';
Yes, java is the username and password is the password here.
Determine the JDBC URL. To connect the MySQL database using Java you need an JDBC URL in the following syntax:
jdbc:mysql://hostname:port/databasename
hostname: The hostname where MySQL server is installed. If it's installed at the same machine where you run the Java code, then you can just use localhost. It can also be an IP address like 127.0.0.1. If you encounter connectivity problems and using 127.0.0.1 instead of localhost solved it, then you've a problem in your network/DNS/hosts config.
port: The TCP/IP port where MySQL server listens on. This is by default 3306.
databasename: The name of the database you'd like to connect to. That's javabase.
So the final URL should look like:
jdbc:mysql://localhost:3306/javabase
Test the connection to MySQL using Java. Create a simple Java class with a main() method to test the connection.
String url = "jdbc:mysql://localhost:3306/javabase";
String username = "java";
String password = "password";
System.out.println("Connecting database...");
try (Connection connection = DriverManager.getConnection(url, username, password)) {
System.out.println("Database connected!");
} catch (SQLException e) {
throw new IllegalStateException("Cannot connect the database!", e);
}
If you get a SQLException: No suitable driver, then it means that either the JDBC driver wasn't autoloaded at all or that the JDBC URL is wrong (i.e. it wasn't recognized by any of the loaded drivers). Normally, a JDBC 4.0 driver should be autoloaded when you just drop it in runtime classpath. To exclude one and other, you can always manually load it as below:
System.out.println("Loading driver...");
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Driver loaded!");
} catch (ClassNotFoundException e) {
throw new IllegalStateException("Cannot find the driver in the classpath!", e);
}
Note that the newInstance() call is not needed here. It's just to fix the old and buggy org.gjt.mm.mysql.Driver. Explanation here. If this line throws ClassNotFoundException, then the JAR file containing the JDBC driver class is simply not been placed in the classpath.
Note that you don't need to load the driver everytime before connecting. Just only once during application startup is enough.
If you get a SQLException: Connection refused or Connection timed out or a MySQL specific CommunicationsException: Communications link failure, then it means that the DB isn't reachable at all. This can have one or more of the following causes:
IP address or hostname in JDBC URL is wrong.
Hostname in JDBC URL is not recognized by local DNS server.
Port number is missing or wrong in JDBC URL.
DB server is down.
DB server doesn't accept TCP/IP connections.
DB server has run out of connections.
Something in between Java and DB is blocking connections, e.g. a firewall or proxy.
To solve the one or the other, follow the following advices:
Verify and test them with ping.
Refresh DNS or use IP address in JDBC URL instead.
Verify it based on my.cnf of MySQL DB.
Start the DB.
Verify if mysqld is started without the --skip-networking option.
Restart the DB and fix your code accordingly that it closes connections in finally.
Disable firewall and/or configure firewall/proxy to allow/forward the port.
Note that closing the Connection is extremely important. If you don't close connections and keep getting a lot of them in a short time, then the database may run out of connections and your application may break. Always acquire the Connection in a try-with-resources statement. Or if you're not on Java 7 yet, explicitly close it in finally of a try-finally block. Closing in finally is just to ensure that it get closed as well in case of an exception. This also applies to Statement, PreparedStatement and ResultSet.
That was it as far the connectivity concerns. You can find here a more advanced tutorial how to load and store fullworthy Java model objects in a database with help of a basic DAO class.
Using a Singleton Pattern for the DB connection is a bad approach. See among other questions: Is it safe to use a static java.sql.Connection instance in a multithreaded system?. This is a #1 starters mistake.
DriverManager is a fairly old way of doing things. The better way is to get a DataSource, either by looking one up that your app server container already configured for you:
Context context = new InitialContext();
DataSource dataSource = (DataSource) context.lookup("java:comp/env/jdbc/myDB");
or instantiating and configuring one from your database driver directly:
MysqlDataSource dataSource = new MysqlDataSource();
dataSource.setUser("scott");
dataSource.setPassword("tiger");
dataSource.setServerName("myDBHost.example.org");
and then obtain connections from it, same as above:
Connection conn = dataSource.getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT ID FROM USERS");
...
rs.close();
stmt.close();
conn.close();
Initialize database constants
Create constant properties database username, password, URL and drivers, polling limit etc.
// init database constants
// com.mysql.jdbc.Driver
private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250"; // set your own limit
Initialize Connection and Properties
Once the connection is established, it is better to store for reuse purpose.
// init connection object
private Connection connection;
// init properties object
private Properties properties;
Create Properties
The properties object hold the connection information, check if it is already set.
// create properties
private Properties getProperties() {
if (properties == null) {
properties = new Properties();
properties.setProperty("user", USERNAME);
properties.setProperty("password", PASSWORD);
properties.setProperty("MaxPooledStatements", MAX_POOL);
}
return properties;
}
Connect the Database
Now connect to database using the constants and properties initialized.
// connect database
public Connection connect() {
if (connection == null) {
try {
Class.forName(DATABASE_DRIVER);
connection = DriverManager.getConnection(DATABASE_URL, getProperties());
} catch (ClassNotFoundException | SQLException e) {
// Java 7+
e.printStackTrace();
}
}
return connection;
}
Disconnect the database
Once you are done with database operations, just close the connection.
// disconnect database
public void disconnect() {
if (connection != null) {
try {
connection.close();
connection = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Everything together
Use this class MysqlConnect directly after changing database_name, username and password etc.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
public class MysqlConnect {
// init database constants
private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250";
// init connection object
private Connection connection;
// init properties object
private Properties properties;
// create properties
private Properties getProperties() {
if (properties == null) {
properties = new Properties();
properties.setProperty("user", USERNAME);
properties.setProperty("password", PASSWORD);
properties.setProperty("MaxPooledStatements", MAX_POOL);
}
return properties;
}
// connect database
public Connection connect() {
if (connection == null) {
try {
Class.forName(DATABASE_DRIVER);
connection = DriverManager.getConnection(DATABASE_URL, getProperties());
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
}
return connection;
}
// disconnect database
public void disconnect() {
if (connection != null) {
try {
connection.close();
connection = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
How to Use?
Initialize the database class.
// !_ note _! this is just init
// it will not create a connection
MysqlConnect mysqlConnect = new MysqlConnect();
Somewhere else in your code ...
String sql = "SELECT * FROM `stackoverflow`";
try {
PreparedStatement statement = mysqlConnect.connect().prepareStatement(sql);
... go on ...
... go on ...
... DONE ....
} catch (SQLException e) {
e.printStackTrace();
} finally {
mysqlConnect.disconnect();
}
This is all :) If anything to improve edit it! Hope this is helpful.
String url = "jdbc:mysql://127.0.0.1:3306/yourdatabase";
String user = "username";
String password = "password";
// Load the Connector/J driver
Class.forName("com.mysql.jdbc.Driver").newInstance();
// Establish connection to MySQL
Connection conn = DriverManager.getConnection(url, user, password);
Here's the very minimum you need to get data out of a MySQL database:
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection conn = DriverManager.getConnection
("jdbc:mysql://localhost:3306/foo", "root", "password");
Statement stmt = conn.createStatement();
stmt.execute("SELECT * FROM `FOO.BAR`");
stmt.close();
conn.close();
Add exception handling, configuration etc. to taste.
you need to have mysql connector jar in your classpath.
in Java JDBC API makes everything with databases. using JDBC we can write Java applications to
1. Send queries or update SQL to DB(any relational Database)
2. Retrieve and process the results from DB
with below three steps we can able to retrieve data from any Database
Connection con = DriverManager.getConnection(
"jdbc:myDriver:DatabaseName",
dBuserName,
dBuserPassword);
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM Table");
while (rs.next()) {
int x = rs.getInt("a");
String s = rs.getString("b");
float f = rs.getFloat("c");
}
You can see all steps to connect MySQL database from Java application here. For other database, you just need to change the driver in first step only. Please make sure that you provide right path to database and correct username and password.
Visit http://apekshit.com/t/51/Steps-to-connect-Database-using-JAVA
MySQL JDBC Connection with useSSL.
private String db_server = BaseMethods.getSystemData("db_server");
private String db_user = BaseMethods.getSystemData("db_user");
private String db_password = BaseMethods.getSystemData("db_password");
private String connectToDb() throws Exception {
String jdbcDriver = "com.mysql.jdbc.Driver";
String dbUrl = "jdbc:mysql://" + db_server +
"?verifyServerCertificate=false" +
"&useSSL=true" +
"&requireSSL=true";
System.setProperty(jdbcDriver, "");
Class.forName(jdbcDriver).newInstance();
Connection conn = DriverManager.getConnection(dbUrl, db_user, db_password);
Statement statement = conn.createStatement();
String query = "SELECT EXTERNAL_ID FROM offer_letter where ID =" + "\"" + letterID + "\"";
ResultSet resultSet = statement.executeQuery(query);
resultSet.next();
return resultSet.getString(1);
}
Short and Sweet code.
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Driver Loaded");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testDB","root","");
//Database Name - testDB, Username - "root", Password - ""
System.out.println("Connected...");
} catch(Exception e) {
e.printStackTrace();
}
For SQL server 2012
try {
String url = "jdbc:sqlserver://KHILAN:1433;databaseName=testDB;user=Khilan;password=Tuxedo123";
//KHILAN is Host and 1433 is port number
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
System.out.println("Driver Loaded");
conn = DriverManager.getConnection(url);
System.out.println("Connected...");
} catch(Exception e) {
e.printStackTrace();
}
Connection I was using some time ago, it was looking like the easiest way, but also there were recommendation to make there if statement- exactly
Connection con = DriverManager.getConnection(
"jdbc:myDriver:DatabaseName",
dBuserName,
dBuserPassword);
if (con != null){
//..handle your code there
}
Or something like in that way :)
Probably there's some case, while getConnection can return null :)
HOW
To set up the Driver to run a quick sample
1. Go to https://dev.mysql.com/downloads/connector/j/, get the latest version of Connector/J
2. Remember to set the classpath to include the path of the connector jar file.
If we don't set it correctly, below errors can occur:
No suitable driver found for jdbc:mysql://127.0.0.1:3306/msystem_development
java.lang.ClassNotFoundException: com.mysql.jdbc:Driver
To set up the CLASSPATH
Method 1: set the CLASSPATH variable.
export CLASSPATH=".:mysql-connector-java-VERSION.jar"
java MyClassFile
In the above command, I have set the CLASSPATH to the current folder and mysql-connector-java-VERSION.jar file. So when the java MyClassFile command executed, java application launcher will try to load all the Java class in CLASSPATH.
And it found the Drive class => BOOM errors was gone.
Method 2:
java -cp .:mysql-connector-java-VERSION.jar MyClassFile
Note: Class.forName("com.mysql.jdbc.Driver"); This is deprecated at this moment 2019 Apr.
Hope this can help someone!
MySql JDBC Connection:
Class.forName("com.mysql.jdbc.Driver");
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/DatabaseName","Username","Password");
Statement stmt=con.createStatement();
stmt = con.createStatement();
ResultSet rs=stmt.executeQuery("Select * from Table");
Short Code
public class DB {
public static Connection c;
public static Connection getConnection() throws Exception {
if (c == null) {
Class.forName("com.mysql.jdbc.Driver");
c =DriverManager.getConnection("jdbc:mysql://localhost:3306/DATABASE", "USERNAME", "Password");
}
return c;
}
// Send data TO Database
public static void setData(String sql) throws Exception {
DB.getConnection().createStatement().executeUpdate(sql);
}
// Get Data From Database
public static ResultSet getData(String sql) throws Exception {
ResultSet rs = DB.getConnection().createStatement().executeQuery(sql);
return rs;
}
}
Download JDBC Driver
Download link (Select platform independent): https://dev.mysql.com/downloads/connector/j/
Move JDBC Driver to C Drive
Unzip the files and move to C:\ drive. Your driver path should be like C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19
Run Your Java
java -cp "C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19.jar" testMySQL.java
testMySQL.java
import java.sql.*;
import java.io.*;
public class testMySQL {
public static void main(String[] args) {
// TODO Auto-generated method stub
try
{
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con=DriverManager.getConnection(
"jdbc:mysql://localhost:3306/db?useSSL=false&useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC","root","");
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery("show databases;");
System.out.println("Connected");
}
catch(Exception e)
{
System.out.println(e);
}
}
}
I have a docker-compose setup to start my SpringBoot application and a MySQL database. If the database starts first, then my application can connect successfully. But if my application starts first, no database exists yet, so the application throws the following exception and exits:
app_1 | 2018-05-27 14:15:03.415 INFO 1 --- [ main]
com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
app_1 | 2018-05-27 14:15:06.770 ERROR 1 --- [ main]
com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Exception during pool initialization
app_1 | com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:
Communications link failure
I could edit my docker-compose file to make sure the database is always up before the application starts up, but I want the application to be able to handle this case on its own, and not immediately exit when it cannot reach the database address.
There are ways to configure the datasource in the application.properties file to make the application reconnect to the database, as answered here and here. But that doesn't work for a startup connection to the datasource.
How can I make my SpringBoot application retry the connection at startup to the database at a given interval until it successfully connects to the database?
Set HikariCP's initializationFailTimeout property to 0 (zero), or a negative number. As documented here:
āinitializationFailTimeout
This property controls whether the pool will "fail fast" if the pool cannot be seeded with an initial connection successfully. Any positive number is taken to be the number of milliseconds to attempt to acquire an initial connection; the application thread will be blocked during this period. If a connection cannot be acquired before this timeout occurs, an exception will be thrown. This timeout is applied after the connectionTimeout period. If the value is zero (0), HikariCP will attempt to obtain and validate a connection. If a connection is obtained, but fails validation, an exception will be thrown and the pool not started. However, if a connection cannot be obtained, the pool will start, but later efforts to obtain a connection may fail. A value less than zero will bypass any initial connection attempt, and the pool will start immediately while trying to obtain connections in the background. Consequently, later efforts to obtain a connection may fail. Default: 1
There is an alternative way to do this, which doesn't rely on a specific Connection Pool library or a specific database. Note that you will need to use spring-retry to achieve the desired behaviour with this approach
First you need to add spring-retry to your dependencies :
<dependency>
<groupId>org.springframework.retry</groupId>
<artifactId>spring-retry</artifactId>
<version>${spring-retry.version}</version>
</dependency>
Then you can create a decorator over DataSource that will extends AbstractDataSource like bellow :
#Slf4j
#RequiredArgsConstructor
public class RetryableDataSource extends AbstractDataSource {
private final DataSource dataSource;
#Override
#Retryable(maxAttempts = 5, backoff = #Backoff(multiplier = 1.3, maxDelay = 10000))
public Connection getConnection() throws SQLException {
log.info("getting connection ...");
return dataSource.getConnection();
}
#Override
#Retryable(maxAttempts = 5, backoff = #Backoff(multiplier = 2.3, maxDelay = 10000))
public Connection getConnection(String username, String password) throws SQLException {
log.info("getting connection by username and password ...");
return dataSource.getConnection(username, password);
}
}
Then you will need to inject this custom DataSource decorator into Spring context by creating a custom BeanPostProcessor :
#Slf4j
#Order(value = Ordered.HIGHEST_PRECEDENCE)
#Component
public class RetryableDatabasePostProcessor implements BeanPostProcessor {
#Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if(bean instanceof DataSource) {
log.info("-----> configuring a retryable datasource for beanName = {}", beanName);
return new RetryableDataSource((DataSource) bean);
}
return bean;
}
#Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
}
Last but not least you will need to enable Spring retry by adding #EnableRetry annotation to spring main class, example :
#EnableRetry
#SpringBootApplication
public class RetryableDbConnectionApplication {
public static void main(String[] args) {
SpringApplication.run(RetryableDbConnectionApplication.class, args);
}
}
Trying to connect to a database on the system automatically.
The database is in the default Derby folder, created via NetBeans.
What I want to do is start the server and connect to the already existing database.
public void startServer() throws Exception {
NetworkServerControl server = new NetworkServerControl();
server.start(prntWrt);
}
#Override
public void start(Stage primaryStage) throws IOException, Exception {
startServer();
Pane root = (Pane) FXMLLoader.load(InteractiveFictionGame2.class.getResource("MainMenu.fxml"));
Scene scene = new Scene(root);
primaryStage.setTitle("MainMenu");
primaryStage.setScene(scene);
primaryStage.setFullScreen(true);
primaryStage.show();
}
It seems that the server does start but for some reason I can't connect to the database as it thinks it is non existant.
String host = "jdbc:derby://localhost:1527/InteractiveGameDatabase";
String unm = "Kylar";
String pswrd = "aswzxc";
public void loadImg() throws IOException {
try {
String SQL = "select vista from location where ycoordinate = ? and xcoordinate = ?";
Stage stage = new Stage();
con = DriverManager.getConnection(host, unm, pswrd);
stmnt = con.prepareStatement(SQL);
stmnt.setInt(1, ycoord);
stmnt.setInt(2, xcoord);
rs = stmnt.executeQuery();
rs.next();
fis = rs.getBinaryStream(1);
BufferedImage imgt = null;
try {
imgt = javax.imageio.ImageIO.read(fis);
} catch (IOException ex) {
System.out.println("Image failed to load.");
}
Image newImg = SwingFXUtils.toFXImage(imgt, null);
fadeInImage();
img_1.setFitHeight(880);
img_1.setImage(newImg);
img_1.setPreserveRatio(true);
img_1.setCache(true);
CountDownLatch doneLatch = new CountDownLatch(1);
animateUsingTimeline();
stck1.getChildren().addAll();
Scene scene = new Scene(stck1);
stage.setTitle("Interactive Fiction Game");
stage.setScene(scene);
stage.setFullScreen(true);
stage.show();
rs.close();
stmnt.close();
con.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
I get an error "The connection was refused because the database InteractiveGameDatabase was not found.". If I start the server through the NetBeans IDE and then run the application everything is perfect. Any help will be appreciated.
Since you specified:
String host = "jdbc:derby://localhost:1527/InteractiveGameDatabase";
as your connection URL, the Derby Network Server is looking for the database using the relative database name "InteractiveGameDatabase". Since that is a relative name, not an absolute name, the Derby Network Server will look for the database in its home directory, which is typically whatever was the current directory when you started the Derby Network Server.
So probably what's going here is that when you run the Derby Network Server in NetBeans, it runs with a certain directory as its home directory, according to how NetBeans starts it up.
But when you run the Derby Network Server yourself, by hand, it runs in a different directory as its home directory, because you didn't precisely start it up in the same directory where NetBeans starts it up, and hence it can't find the database InteractiveGameDatabase in this new directory.
You could:
Always use the NetBeans-started Derby Network Server
Start your own Network Server, but arrange to do so in the same directory where NetBeans starts the Derby Network Server
Start your own Network Server, but change your connection URL to specify the full absolute path to the location where the NetBeans-started Derby Network Server was run, so that your Network Server can access that directory when you go to open the database.
There are many other possibilities, but hopefully these are enough to give you an idea about what's going on.
I am new to JDBC and I am trying to make a connection to a MySQL database.
I am using Connector/J driver, but I cant find the JDBC connection string for my Class.forName() method.
Assuming your driver is in path,
String url = "jdbc:mysql://localhost/test";
Class.forName ("com.mysql.jdbc.Driver").newInstance ();
Connection conn = DriverManager.getConnection (url, "username", "password");
Here's the documentation:
https://dev.mysql.com/doc/connector-j/en/connector-j-reference-configuration-properties.html
A basic connection string looks like:
jdbc:mysql://localhost:3306/dbname
The class.forName string is "com.mysql.jdbc.Driver", which you can find (edit: now on the same page).
"jdbc:mysql://localhost"
From the oracle docs..
jdbc:mysql://[host][,failoverhost...]
[:port]/[database]
[?propertyName1][=propertyValue1]
[&propertyName2][=propertyValue2]
host:port is the host name and port number of the computer hosting your database. If not specified, the default values of host and port are 127.0.0.1 and 3306, respectively.
database is the name of the database to connect to. If not specified, a connection is made with no default database.
failover is the name of a standby database (MySQL Connector/J supports failover).
propertyName=propertyValue represents an optional, ampersand-separated list of properties. These attributes enable you to instruct MySQL Connector/J to perform various tasks.
It is very simple :
Go to MySQL workbench and lookup for Database > Manage Connections
you will see a list of connections. Click on the connection you wish to connect to.
You will see a tabs around connection, remote management, system profile. Click on connection tab.
your url is jdbc:mysql://<hostname>:<port>/<dbname>?prop1 etc.
where <hostname> and <port> are given in the connection tab.It will mostly be localhost : 3306. <dbname> will be found under System Profile tab in Windows Service Name. Default will mostly be MySQL5<x> where x is the version number eg. 56 for MySQL5.6 and 55 for MySQL5.5 etc.You can specify ur own Windows Service name to connect too.
Construct the url accordingly and set the url to connect.
For Mysql, the jdbc Driver connection string is com.mysql.jdbc.Driver. Use the following code to get connected:-
class DBConnection {
private static Connection con = null;
private static String USERNAME = "your_mysql_username";
private static String PASSWORD = "your_mysql_password";
private static String DRIVER = "com.mysql.jdbc.Driver";
private static String URL = "jdbc:mysql://localhost:3306/database_name";
public static Connection getDatabaseConnection(){
Class.forName(DRIVER);
return con = DriverManager.getConnection(URL,USERNAME,PASSWORD);
}
}
As the answer seems already been answered, there is not much to add but I would like to add one thing to the existing answers.
This was the way of loading class for JDBC driver for mysql
com.mysql.jdbc.Driver
But this is deprecated now. The new driver class is now
com.mysql.cj.jdbc.Driver
Also the driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
update for mySQL 8 :
String jdbcUrl="jdbc:mysql://localhost:3306/youdatabase?useSSL=false&serverTimezone=UTC";
Here is a little code from my side :)
needed driver:
com.mysql.jdbc.Driver
download: here (Platform Independent)
connection string in one line:
jdbc:mysql://localhost:3306/db-name?user=user_name&password=db_password&useSSL=false
example code:
public static void testDB(){
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
try {
Connection connection = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/db-name?user=user_name&password=db_password&useSSL=false");
if (connection != null) {
Statement statement = connection.createStatement();
if (statement != null) {
ResultSet resultSet = statement.executeQuery("select * from test");
if (resultSet != null) {
ResultSetMetaData meta = resultSet.getMetaData();
int length = meta.getColumnCount();
while(resultSet.next())
{
for(int i = 1; i <= length; i++){
System.out.println(meta.getColumnName(i) + ": " + resultSet.getString(meta.getColumnName(i)));
}
}
resultSet.close();
}
statement.close();
}
connection.close();
}
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
update for mySQL 8 :
String jdbcUrl="jdbc:mysql://localhost:3306/youdatabase?useSSL=false&serverTimezone=UTC";
Check whether your Jdbc configurations and URL correct or wrong using the following code snippet.
import java.sql.Connection;
import java.sql.DriverManager;
public class TestJdbc {
public static void main(String[] args) {
//db name:testdb_version001
//useSSL=false (get rid of MySQL SSL warnings)
String jdbcUrl = "jdbc:mysql://localhost:3306/testdb_version001?useSSL=false";
String username="testdb";
String password ="testdb";
try{
System.out.println("Connecting to database :" +jdbcUrl);
Connection myConn =
DriverManager.getConnection(jdbcUrl,username,password);
System.out.println("Connection Successful...!");
}catch (Exception e){
e.printStackTrace();
//e.printStackTrace();
}
}
}
The method Class.forName() is used to register the JDBC driver. A connection string is used to retrieve the connection to the database.
The way to retrieve the connection to the database is shown below. Ideally since you do not want to create multiple connections to the database, limit the connections to one and re-use the same connection. Therefore use the singleton pattern here when handling connections to the database.
Shown Below shows a connection string with the retrieval of the connection:
public class Database {
private String URL = "jdbc:mysql://localhost:3306/your_db_name"; //database url
private String username = ""; //database username
private String password = ""; //database password
private static Database theDatabase = new Database();
private Connection theConnection;
private Database(){
try{
Class.forName("com.mysql.jdbc.Driver"); //setting classname of JDBC Driver
this.theConnection = DriverManager.getConnection(URL, username, password);
} catch(Exception ex){
System.out.println("Error Connecting to Database: "+ex);
}
}
public static Database getDatabaseInstance(){
return theDatabase;
}
public Connection getTheConnectionObject(){
return theConnection;
}
}
String url = "jdbc:mysql://localhost:3306/dbname";
String user = "user";
String pass = "pass";
Class.forName ("com.mysql.jdbc.Driver").newInstance ();
Connection conn = DriverManager.getConnection (url, user, pass);
3306 is the default port for mysql.
If you are using Java 7 then there is no need to even add the Class.forName("com.mysql.jdbc.Driver").newInstance (); statement.Automatic Resource Management (ARM) is added in JDBC 4.1 which comes by default in Java 7.
The general format for a JDBC URL for connecting to a MySQL server is as follows, with items in square brackets ([ ]) being optional:
jdbc:mysql://[host1][:port1][,[host2][:port2]]...[/[database]] Ā»
[?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
protocol//[hosts][/database][?properties]
If you don't have any properties ignore it then it will be like
jdbc:mysql://127.0.0.1:3306/test
jdbc:mysql is the protocol
127.0.0.1: is the host and 3306 is the port number
test is the database
it's depends on what service you're using.
if you use MySQL Workbench it wold be some thing like this :
jdbc:mysql://"host":"port number"/
String url = "jdbc:mysql://localhost:3306/";
And of course it will be different if you using SSL/SSH.
For more information follow the official link of Jetbriens (intelliJ idea) :
Connecting to a database #
https://www.jetbrains.com/help/idea/connecting-to-a-database.html
Configuring database connections #
https://www.jetbrains.com/help/idea/configuring-database-connections.html
Check if the Driver Connector jar matches the SQL version.
I was also getting the same error as I was using the
mySQl-connector-java-5.1.30.jar
with MySql 8