Why are my characters replaced with \'?\' when saving data in my Java web application?

JDBC Character Encoding Issue Resolved in Java Web Application

In a Java web application deployed on GlassFish 3 and utilizing JPA (EclipseLink) with a MySQL database, a user encountered encoding discrepancies when saving data through the update() method. Characters in string fields were replaced with '?' symbols upon database insertion.

Despite configuring the server, web pages, and database to use UTF-8, the issue persisted. While the data was displayed correctly on subsequent pages and appeared valid during NetBeans debugging, doubts remained about the accuracy of the debug translation.

JDBC Configuration the Culprit

Tracing the root cause, it was discovered that JDBC, rather than JPA, governs character encoding in this scenario. By appending the following parameter to the JDBC connection URL:

characterEncoding=utf8

the encoding issue was resolved. The modified connection URL ensures that UTF-8 character encoding is explicitly defined for JDBC communication with the MySQL database, resolving the integrity issue in string fields.

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