Java Spring JPA Hibernate 不更新列

Question

I'm using Spring 4.1.0 with hibernate-entitymanager 4.1.9

Also, I'm using Postgres 9.6

I have following entity:

@Entity
@Table(name = "audit", schema = "public")
@SequenceGenerator(name = "AUDIT_SEQUENCE", sequenceName = "AUDIT_SEQUENCE", allocationSize = 1, initialValue = 1)
public class AuditTrail {

        @Id
        @Column(name = "auditid", unique = true)
        @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "AUDIT_SEQUENCE")
        private long auditId;

        @Column(name = "auditvalue")
        private String auditValue;


        ... getter setters ...
}

This gives the column structure as character varying(255)

I want to update the auditValue column to have length 10000. So I update the entity as:

@Column(name = "auditvalue", length = 10000)
private String auditValue;

But the column structure does not update.

My applicationContext.xml contains:

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="com.avaya.mediamanager.entity" />
    <property name="jpaVendorAdapter" ref="hbAdapterBean_pgsql"/>   
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.show_sql">false</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.hbm2ddl.auto">update</prop>
            <prop key="hibernate.id.new_generator_mappings">true</prop>
        </props>
    </property>     
</bean>
<bean id="hbAdapterBean_pgsql" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">  
    <property name="showSql" value="false"></property>  
    <property name="generateDdl" value="true"></property>  
    <property name="databasePlatform" value="org.hibernate.dialect.PostgreSQLDialect"></property>  
</bean>  

How can I get the column updated from the application?

Answer 1

From what i'm understanding, hibernate.hbm2ddl.auto set to update doesn't actually update already created tables, but will add new one without dropping your data.

You could change hibernate.hbm2ddl.auto to create-drop , this will cause your schema to be recreated each time you restart your service, but I not sure if it's exactly what you want since it will also drop all your data.

If you want to keep your data, you might need to think about using something like flyway to populate it.

I hope this help! Have fun!

Answer 2

I agree with @Schisme From what I know, it's not possible to update type or delete columns. You will need to use flyway, and create a migration.

In order to make things easier you can create a mysql procedure inside migration like this:

DELIMITER $$
CREATE PROCEDURE change_column_type_if_exists(`@TABLE` VARCHAR(100), `@COLUMN` VARCHAR(100), `@NEW_TYPE` varchar(100) )
`DropColumnIfExists`: BEGIN
    DECLARE `@EXISTS` INT UNSIGNED DEFAULT 0;

    SELECT COUNT(*) INTO `@EXISTS`
    FROM `information_schema`.`columns`
    WHERE (
                      `TABLE_SCHEMA` = DATABASE()
                  AND `TABLE_NAME` = `@TABLE`
                  AND `COLUMN_NAME` = `@COLUMN`
              );

    IF (`@EXISTS` > 0) THEN
        SET @SQL = CONCAT('ALTER TABLE ', `@TABLE`, ' modify ', `@COLUMN`, ' ',`@NEW_TYPE`,' ;');
        PREPARE query FROM @SQL;
        EXECUTE query;
    END IF;
END $$
DELIMITER ;

And then in case you have a column you need to modify type for, to run something like this:

CALL change_column_type_if_exists('audit', 'auditvalue', 'varchar(3000)');

or

CALL change_column_type_if_exists('audit', 'auditvalue', 'TEXT');

If you found any better alternatives, please let us know too. We would appreciate it.