Add a column to all MySQL Select Queries in a single shot

Question

Trying to add a comment to all MySQL Select Queries in my web application at runtime.

For example, the original queries in the code looks like:

select a,         


        

Answer 1

Create a Custom DB Interceptor

package com.felix.dao.interceptor;
import org.hibernate.EmptyInterceptor;

public class CustomDBInterceptor extends EmptyInterceptor {

  @Override
  public String onPrepareStatement(String sql) {
    String commentStr = "/*Comment*/"
    return super.onPrepareStatement(commentStr+sql);
  }

}

In the Spring Context file, configure the Interceptor for the session factory:

<bean id="customDBInterceptor" class="com.felix.dao.interceptor.CustomDBInterceptor"/>
<bean id="sessionFactory"
    class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="datasource" />
    <property name="entityInterceptor">
        <ref bean="customDBInterceptor"/>
    </property>
    ...
</bean>

Make sure the Custom DB Interceptor does not have a cyclic dependency on the sessionFactory. With the above, all queries fired through the session factory, are intercepted, modified and then passed to the onPrepareStatement method.

Answer 2

If your goal is to add an extra column with a constant value, try giving it an alias:

SELECT a, b, c, "TESTVALUE" AS `new_column` FROM ...