How Can I Call Stored Procedures in Java Using JPA?

Call stored procedures in Java and JPA

Storing business logic in stored procedures improves performance and code maintainability. This article explores two methods of calling stored procedures from Java using JPA: the CallableStatement method and JPA 2.1 StoredProcedureQuery.

CallableStatement method

The CallableStatement class provides a versatile method for calling stored procedures. It allows you to specify input parameters and retrieve output parameters or result sets. However, it requires manual mapping between SQL types and Java objects, which can be tedious.

JPA 2.1 StoredProcedureQuery

JPA 2.1 introduced built-in support for calling stored procedures. The StoredProcedureQuery class simplifies this process by allowing you to pass input parameters and specify a result class or resultSetMapping.

Use JPA StoredProcedureQuery to call the "getEmployeeDetails" stored procedure:

<code class="language-java">Query query = em.createNativeQuery("{call getEmployeeDetails(?,?)}", EmployeeDetails.class)
    .setParameter(1, employeeId)
    .setParameter(2, companyId);

List<EmployeeDetails> result = query.getResultList();</code>

Advantages of using JPA to call stored procedures

• Type safety and automatic mapping: JPA handles conversion between SQL and Java types, ensuring data integrity.
• Simple API: The StoredProcedureQuery interface simplifies the process of executing and retrieving stored procedure results.
• Support for named parameters: You can explicitly name input parameters in NativeQuery to avoid confusion or errors.

SQL statements that call stored procedures

The correct SQL statement to call a stored procedure is:

<code class="language-sql">{call getEmployeeDetails(?,?)}</code>

Note: Enclose the stored procedure name in curly braces and separate parameters with commas and question marks (?).

Other notes:

• If the stored procedure returns a result set, use getSingleResult() with caution as it may fail even if it only expects a single row.
• Pass resultSetMapping name or result class details to map result set to Java object.
• Parameter names may not work in all cases, so try using parameter indexes instead.

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