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5.2 Connection URL Syntax

This section explains the syntax of the URLs for connecting to MySQL.

This is the generic format of the connection URL:


The URL consists of the following parts:


Any reserved characters for URLs (for example, /, :, @, (, ), [, ], &, #, =, ?, and space) that appear in any part of the connection URL must be percent encoded.


There are three possible protocols for a connection:


Depending on the situation, the hosts part may consist simply of a host name, or it can be a complex structure consisting of various elements like multiple host names, port numbers, host-specific properties, and user credentials.

  • Single host:

    • Single-host connections without adding host-specific properties:

      • The hosts part is written in the format of host:port. This is an example of a simple single-host connection URL:

      • When host is not specified, the default value of localhost is used.

      • port is a standard port number, i.e., an integer between 1 and 65535. The default port number for an ordinary MySQL connection is 3306. If port is not specified, the default value is used.

    • Single-host connections adding host-specific properties:

      • The host is defined as a succession of key=value pairs. Keys are used to identify the host, the port, as well as any host-specific properties, and they are preceded by address=:


        Here is a sample URL:


        This is the mandatory format for iPv6 addresses, but it also supports the iPv4 addresses.

      • The host and the port are identified by the keys host and port. The description of the default values of host and port in Single host without host-specific properties above also applies here.

      • Other keys that can be added include user, password, protocol, and so on. They override the global values set in the properties part of the URL. Limit the overrides to user, password, network timeouts, and statement and metadata cache sizes; the effects of other per-host overrides are not defined.

      • key is case-sensitive. Two keys differing in case only are considered conflicting, and there are no guarantees on which one will be used.

  • Multiple hosts

    • Specify multiple hosts by listing them in a comma-separated list:


      Each host can be specified in any of the two ways described in Single host above. Here are some examples:

  • User credentials

    User credentials can be set outside of the connection URL—for example, as arguments when getting a connection from the java.sql.DriverManager (see Section 5.3, “Configuration Properties for Connector/J” for details). When set with the connection URL, use the keys user and password to specify credentials for each host:


    For example:


    When multiple user credentials are specified, the one to the left takes precedence—that is, going from left to right in the connection string, the first one found that is applicable to a host is the one that is used.


The default database or catalog to open. If the database is not specified, the connection is made with no default database. In this case, either call the setCatalog() method on the Connection instance, or specify table names using the database name (that is, SELECT dbname.tablename.colname FROM dbname.tablename...) in your SQL statements. Opening a connection without specifying the database to use is, in general, only useful when building tools that work with multiple databases, such as GUI database managers.


Always use the Connection.setCatalog() method to specify the desired database in JDBC applications, rather than the USE database statement.


A succession of global properties applying to all hosts, preceded by ? and written as key=value pairs separated by the symbol &. Here are some examples:


The following are true for the key-value pairs:

  • key and value are just strings. Proper type conversion and validation are performed internally in Connector/J.

  • key is case-sensitive. Two keys differing in case only are considered conflicting, and it is uncertain which one will be used.

  • Any host-specific values specified with key-value pairs as explained in Single host with host-specific properties and Multiple hosts above override the global values set here.