Solve the JDBC Chinese problem of MySQL in Linux

In addition to the well-known Chinese characters, mysql instances on Linux may encounter the following problems:

You use mysql5x and configure the database to use the UTF-8 character set, you use the linux Standard jdk environment, you use a high enough mysql jdbc driver, you use the UTF-8 character set as the basic character set for J2EE. You use a standard CharacterEncodingFilter to complete Transparent Character Set conversion.

In this way, in most cases, you have not felt the interference of Chinese characters on Java applications. However, when saving a form, you find that Chinese characters are saved as garbled characters or question marks.

The reason is that this is a known BUG of the mysql driver. I failed to find (not looking for) the original BUG report, but it means, jdbc driver may not be able to correctly identify the dash character in the jdbc url.

If you specify the default collation type to the UTF-8 for the test database (for example, alter database test character set utf8 ;), reading data from the database can automatically adopt the correct decoding sequence. Therefore, your Java application looks so normal under the "read-only" status, this issue is not exposed until you try to submit the form.

The solution is to replace "UTF-8" in the URL with "UTF8" to avoid the above traps.

In addition, the jdbc url separates parameters by the "&" character instead of the "&" character. If you write "&" in the URL, the following parameters cannot be correctly applied to the driver layer. This problem is complicated because you may need to escape the code when writing URLs in different locations:

1. when writing a URL in an xml file, add & Because xml considers & as the escape character, so when you write user = root & password = xxx to xml, it is equivalent to Writing user = root & password = xxx in java source code.

2. When writing a URL in the properties file, & there is no escape meaning. Therefore, the URL format is basically the same as that in the Java source code. The so-called basic consistency involves another special character ":". In properties, it is optional to use the escape sequence "\:" to indicate a ":", that is, many times, you can mix these two formats.