Is it possible to set a default value for columns in JPA, and if, how is it done using annotations?
This question is related to
java
jpa
annotations
In my case, I modified hibernate-core source code, well, to introduce a new annotation @DefaultValue:
commit 34199cba96b6b1dc42d0d19c066bd4d119b553d5
Author: Lenik <xjl at 99jsj.com>
Date: Wed Dec 21 13:28:33 2011 +0800
Add default-value ddl support with annotation @DefaultValue.
diff --git a/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java b/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java
new file mode 100644
index 0000000..b3e605e
--- /dev/null
+++ b/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java
@@ -0,0 +1,35 @@
+package org.hibernate.annotations;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+
+/**
+ * Specify a default value for the column.
+ *
+ * This is used to generate the auto DDL.
+ *
+ * WARNING: This is not part of JPA 2.0 specification.
+ *
+ * @author ???
+ */
[email protected]({ FIELD, METHOD })
+@Retention(RUNTIME)
+public @interface DefaultValue {
+
+ /**
+ * The default value sql fragment.
+ *
+ * For string values, you need to quote the value like 'foo'.
+ *
+ * Because different database implementation may use different
+ * quoting format, so this is not portable. But for simple values
+ * like number and strings, this is generally enough for use.
+ */
+ String value();
+
+}
diff --git a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
index b289b1e..ac57f1a 100644
--- a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
+++ b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
@@ -29,6 +29,7 @@ import org.hibernate.AnnotationException;
import org.hibernate.AssertionFailure;
import org.hibernate.annotations.ColumnTransformer;
import org.hibernate.annotations.ColumnTransformers;
+import org.hibernate.annotations.DefaultValue;
import org.hibernate.annotations.common.reflection.XProperty;
import org.hibernate.cfg.annotations.Nullability;
import org.hibernate.mapping.Column;
@@ -65,6 +66,7 @@ public class Ejb3Column {
private String propertyName;
private boolean unique;
private boolean nullable = true;
+ private String defaultValue;
private String formulaString;
private Formula formula;
private Table table;
@@ -175,7 +177,15 @@ public class Ejb3Column {
return mappingColumn.isNullable();
}
- public Ejb3Column() {
+ public String getDefaultValue() {
+ return defaultValue;
+ }
+
+ public void setDefaultValue(String defaultValue) {
+ this.defaultValue = defaultValue;
+ }
+
+ public Ejb3Column() {
}
public void bind() {
@@ -186,7 +196,7 @@ public class Ejb3Column {
}
else {
initMappingColumn(
- logicalColumnName, propertyName, length, precision, scale, nullable, sqlType, unique, true
+ logicalColumnName, propertyName, length, precision, scale, nullable, sqlType, unique, defaultValue, true
);
log.debug( "Binding column: " + toString());
}
@@ -201,6 +211,7 @@ public class Ejb3Column {
boolean nullable,
String sqlType,
boolean unique,
+ String defaultValue,
boolean applyNamingStrategy) {
if ( StringHelper.isNotEmpty( formulaString ) ) {
this.formula = new Formula();
@@ -217,6 +228,7 @@ public class Ejb3Column {
this.mappingColumn.setNullable( nullable );
this.mappingColumn.setSqlType( sqlType );
this.mappingColumn.setUnique( unique );
+ this.mappingColumn.setDefaultValue(defaultValue);
if(writeExpression != null && !writeExpression.matches("[^?]*\\?[^?]*")) {
throw new AnnotationException(
@@ -454,6 +466,11 @@ public class Ejb3Column {
else {
column.setLogicalColumnName( columnName );
}
+ DefaultValue _defaultValue = inferredData.getProperty().getAnnotation(DefaultValue.class);
+ if (_defaultValue != null) {
+ String defaultValue = _defaultValue.value();
+ column.setDefaultValue(defaultValue);
+ }
column.setPropertyName(
BinderHelper.getRelativePath( propertyHolder, inferredData.getPropertyName() )
diff --git a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
index e57636a..3d871f7 100644
--- a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
+++ b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
@@ -423,6 +424,7 @@ public class Ejb3JoinColumn extends Ejb3Column {
getMappingColumn() != null ? getMappingColumn().isNullable() : false,
referencedColumn.getSqlType(),
getMappingColumn() != null ? getMappingColumn().isUnique() : false,
+ null, // default-value
false
);
linkWithValue( value );
@@ -502,6 +504,7 @@ public class Ejb3JoinColumn extends Ejb3Column {
getMappingColumn().isNullable(),
column.getSqlType(),
getMappingColumn().isUnique(),
+ null, // default-value
false //We do copy no strategy here
);
linkWithValue( value );
Well, this is a hibernate-only solution.
If you're using a double, you can use the following:
@Column(columnDefinition="double precision default '96'")
private Double grolsh;
Yes it's db specific.
This isn't possible in JPA.
Here's what you can do with the Column annotation: http://java.sun.com/javaee/5/docs/api/javax/persistence/Column.html
If you're using a double, you can use the following:
@Column(columnDefinition="double precision default '96'")
private Double grolsh;
Yes it's db specific.
another approach is using javax.persistence.PrePersist
@PrePersist
void preInsert() {
if (this.createdTime == null)
this.createdTime = new Date();
}
You can't do this with the column annotation. I think the only way is to set the default value when a object is created. Maybe the default constructor would be the right place to do that.
@Column(columnDefinition='...') doesn't work when you set the default constraint in database while inserting the data.insertable = false and remove columnDefinition='...' from annotation, then database will automatically insert the default value from the database.insertable = false in Hibernate/JPA, it will work.Neither JPA nor Hibernate annotations support the notion of a default column value. As a workaround to this limitation, set all default values just before you invoke a Hibernate save() or update() on the session. This closely as possible (short of Hibernate setting the default values) mimics the behaviour of the database which sets default values when it saves a row in a table.
Unlike setting the default values in the model class as this alternative answer suggests, this approach also ensures that criteria queries that use an Example object as a prototype for the search will continue to work as before. When you set the default value of a nullable attribute (one that has a non-primitive type) in a model class, a Hibernate query-by-example will no longer ignore the associated column where previously it would ignore it because it was null.
you can use the java reflect api:
@PrePersist
void preInsert() {
PrePersistUtil.pre(this);
}
This is common:
public class PrePersistUtil {
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
public static void pre(Object object){
try {
Field[] fields = object.getClass().getDeclaredFields();
for(Field field : fields){
field.setAccessible(true);
if (field.getType().getName().equals("java.lang.Long")
&& field.get(object) == null){
field.set(object,0L);
}else if (field.getType().getName().equals("java.lang.String")
&& field.get(object) == null){
field.set(object,"");
}else if (field.getType().getName().equals("java.util.Date")
&& field.get(object) == null){
field.set(object,sdf.parse("1900-01-01"));
}else if (field.getType().getName().equals("java.lang.Double")
&& field.get(object) == null){
field.set(object,0.0d);
}else if (field.getType().getName().equals("java.lang.Integer")
&& field.get(object) == null){
field.set(object,0);
}else if (field.getType().getName().equals("java.lang.Float")
&& field.get(object) == null){
field.set(object,0.0f);
}
}
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
}
}
@Column(columnDefinition='...') doesn't work when you set the default constraint in database while inserting the data.insertable = false and remove columnDefinition='...' from annotation, then database will automatically insert the default value from the database.insertable = false in Hibernate/JPA, it will work.I use columnDefinition and it works very good
@Column(columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
private Date createdDate;
You can define the default value in the database designer, or when you create the table. For instance in SQL Server you can set the default vault of a Date field to (getDate()). Use insertable=false as mentioned in your column definition. JPA will not specify that column on inserts and the database will generate the value for you.
@Column(columnDefinition="tinyint(1) default 1")
I just tested the issue. It works just fine. Thanks for the hint.
About the comments:
@Column(name="price")
private double price = 0.0;
This one doesn't set the default column value in the database (of course).
I use columnDefinition and it works very good
@Column(columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
private Date createdDate;
You can do the following:
@Column(name="price")
private double price = 0.0;
There! You've just used zero as the default value.
Note this will serve you if you're only accessing the database from this application. If other applications also use the database, then you should make this check from the database using Cameron's columnDefinition annotation attribute, or some other way.
@PrePersist
void preInsert() {
if (this.dateOfConsent == null)
this.dateOfConsent = LocalDateTime.now();
if(this.consentExpiry==null)
this.consentExpiry = this.dateOfConsent.plusMonths(3);
}
In my case due to the field being LocalDateTime i used this, it is recommended due to vendor independence
In 2017, JPA 2.1 still has only @Column(columnDefinition='...') to which you put the literal SQL definition of the column. Which is quite unflexible and forces you to also declare the other aspects like type, short-circuiting the JPA implementation's view on that matter.
Hibernate though, has this:
@Column(length = 4096, nullable = false)
@org.hibernate.annotations.ColumnDefault("")
private String description;
Identifies the DEFAULT value to apply to the associated column via DDL.
Two notes to that:
1) Don't be afraid of going non-standard. Working as a JBoss developer, I've seen quite some specification processes. The specification is basically the baseline that the big players in given field are willing to commit to support for the next decade or so. It's true for security, for messaging, ORM is no difference (although JPA covers quite a lot). My experience as a developer is that in a complex application, sooner or later you will need a non-standard API anyway. And @ColumnDefault is an example when it outweigts the negatives of using a non-standard solution.
2) It's nice how everyone waves @PrePersist or constructor member initialization. But that's NOT the same. How about bulk SQL updates? How about statements that don't set the column? DEFAULT has it's role and that's not substitutable by initializing a Java class member.
you can use the java reflect api:
@PrePersist
void preInsert() {
PrePersistUtil.pre(this);
}
This is common:
public class PrePersistUtil {
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
public static void pre(Object object){
try {
Field[] fields = object.getClass().getDeclaredFields();
for(Field field : fields){
field.setAccessible(true);
if (field.getType().getName().equals("java.lang.Long")
&& field.get(object) == null){
field.set(object,0L);
}else if (field.getType().getName().equals("java.lang.String")
&& field.get(object) == null){
field.set(object,"");
}else if (field.getType().getName().equals("java.util.Date")
&& field.get(object) == null){
field.set(object,sdf.parse("1900-01-01"));
}else if (field.getType().getName().equals("java.lang.Double")
&& field.get(object) == null){
field.set(object,0.0d);
}else if (field.getType().getName().equals("java.lang.Integer")
&& field.get(object) == null){
field.set(object,0);
}else if (field.getType().getName().equals("java.lang.Float")
&& field.get(object) == null){
field.set(object,0.0f);
}
}
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
}
}
You can't do this with the column annotation. I think the only way is to set the default value when a object is created. Maybe the default constructor would be the right place to do that.
Seeing as I stumbled upon this from Google while trying to solve the very same problem, I'm just gonna throw in the solution I cooked up in case someone finds it useful.
From my point of view there's really only 1 solutions to this problem -- @PrePersist. If you do it in @PrePersist, you gotta check if the value's been set already though.
In 2017, JPA 2.1 still has only @Column(columnDefinition='...') to which you put the literal SQL definition of the column. Which is quite unflexible and forces you to also declare the other aspects like type, short-circuiting the JPA implementation's view on that matter.
Hibernate though, has this:
@Column(length = 4096, nullable = false)
@org.hibernate.annotations.ColumnDefault("")
private String description;
Identifies the DEFAULT value to apply to the associated column via DDL.
Two notes to that:
1) Don't be afraid of going non-standard. Working as a JBoss developer, I've seen quite some specification processes. The specification is basically the baseline that the big players in given field are willing to commit to support for the next decade or so. It's true for security, for messaging, ORM is no difference (although JPA covers quite a lot). My experience as a developer is that in a complex application, sooner or later you will need a non-standard API anyway. And @ColumnDefault is an example when it outweigts the negatives of using a non-standard solution.
2) It's nice how everyone waves @PrePersist or constructor member initialization. But that's NOT the same. How about bulk SQL updates? How about statements that don't set the column? DEFAULT has it's role and that's not substitutable by initializing a Java class member.
JPA doesn't support that and it would be useful if it did. Using columnDefinition is DB-specific and not acceptable in many cases. setting a default in the class is not enough when you retrieve a record having null values (which typically happens when you re-run old DBUnit tests). What I do is this:
public class MyObject
{
int attrib = 0;
/** Default is 0 */
@Column ( nullable = true )
public int getAttrib()
/** Falls to default = 0 when null */
public void setAttrib ( Integer attrib ) {
this.attrib = attrib == null ? 0 : attrib;
}
}
Java auto-boxing helps a lot in that.
another approach is using javax.persistence.PrePersist
@PrePersist
void preInsert() {
if (this.createdTime == null)
this.createdTime = new Date();
}
Neither JPA nor Hibernate annotations support the notion of a default column value. As a workaround to this limitation, set all default values just before you invoke a Hibernate save() or update() on the session. This closely as possible (short of Hibernate setting the default values) mimics the behaviour of the database which sets default values when it saves a row in a table.
Unlike setting the default values in the model class as this alternative answer suggests, this approach also ensures that criteria queries that use an Example object as a prototype for the search will continue to work as before. When you set the default value of a nullable attribute (one that has a non-primitive type) in a model class, a Hibernate query-by-example will no longer ignore the associated column where previously it would ignore it because it was null.
This isn't possible in JPA.
Here's what you can do with the Column annotation: http://java.sun.com/javaee/5/docs/api/javax/persistence/Column.html
In my case, I modified hibernate-core source code, well, to introduce a new annotation @DefaultValue:
commit 34199cba96b6b1dc42d0d19c066bd4d119b553d5
Author: Lenik <xjl at 99jsj.com>
Date: Wed Dec 21 13:28:33 2011 +0800
Add default-value ddl support with annotation @DefaultValue.
diff --git a/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java b/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java
new file mode 100644
index 0000000..b3e605e
--- /dev/null
+++ b/hibernate-core/src/main/java/org/hibernate/annotations/DefaultValue.java
@@ -0,0 +1,35 @@
+package org.hibernate.annotations;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+
+/**
+ * Specify a default value for the column.
+ *
+ * This is used to generate the auto DDL.
+ *
+ * WARNING: This is not part of JPA 2.0 specification.
+ *
+ * @author ???
+ */
[email protected]({ FIELD, METHOD })
+@Retention(RUNTIME)
+public @interface DefaultValue {
+
+ /**
+ * The default value sql fragment.
+ *
+ * For string values, you need to quote the value like 'foo'.
+ *
+ * Because different database implementation may use different
+ * quoting format, so this is not portable. But for simple values
+ * like number and strings, this is generally enough for use.
+ */
+ String value();
+
+}
diff --git a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
index b289b1e..ac57f1a 100644
--- a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
+++ b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3Column.java
@@ -29,6 +29,7 @@ import org.hibernate.AnnotationException;
import org.hibernate.AssertionFailure;
import org.hibernate.annotations.ColumnTransformer;
import org.hibernate.annotations.ColumnTransformers;
+import org.hibernate.annotations.DefaultValue;
import org.hibernate.annotations.common.reflection.XProperty;
import org.hibernate.cfg.annotations.Nullability;
import org.hibernate.mapping.Column;
@@ -65,6 +66,7 @@ public class Ejb3Column {
private String propertyName;
private boolean unique;
private boolean nullable = true;
+ private String defaultValue;
private String formulaString;
private Formula formula;
private Table table;
@@ -175,7 +177,15 @@ public class Ejb3Column {
return mappingColumn.isNullable();
}
- public Ejb3Column() {
+ public String getDefaultValue() {
+ return defaultValue;
+ }
+
+ public void setDefaultValue(String defaultValue) {
+ this.defaultValue = defaultValue;
+ }
+
+ public Ejb3Column() {
}
public void bind() {
@@ -186,7 +196,7 @@ public class Ejb3Column {
}
else {
initMappingColumn(
- logicalColumnName, propertyName, length, precision, scale, nullable, sqlType, unique, true
+ logicalColumnName, propertyName, length, precision, scale, nullable, sqlType, unique, defaultValue, true
);
log.debug( "Binding column: " + toString());
}
@@ -201,6 +211,7 @@ public class Ejb3Column {
boolean nullable,
String sqlType,
boolean unique,
+ String defaultValue,
boolean applyNamingStrategy) {
if ( StringHelper.isNotEmpty( formulaString ) ) {
this.formula = new Formula();
@@ -217,6 +228,7 @@ public class Ejb3Column {
this.mappingColumn.setNullable( nullable );
this.mappingColumn.setSqlType( sqlType );
this.mappingColumn.setUnique( unique );
+ this.mappingColumn.setDefaultValue(defaultValue);
if(writeExpression != null && !writeExpression.matches("[^?]*\\?[^?]*")) {
throw new AnnotationException(
@@ -454,6 +466,11 @@ public class Ejb3Column {
else {
column.setLogicalColumnName( columnName );
}
+ DefaultValue _defaultValue = inferredData.getProperty().getAnnotation(DefaultValue.class);
+ if (_defaultValue != null) {
+ String defaultValue = _defaultValue.value();
+ column.setDefaultValue(defaultValue);
+ }
column.setPropertyName(
BinderHelper.getRelativePath( propertyHolder, inferredData.getPropertyName() )
diff --git a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
index e57636a..3d871f7 100644
--- a/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
+++ b/hibernate-core/src/main/java/org/hibernate/cfg/Ejb3JoinColumn.java
@@ -423,6 +424,7 @@ public class Ejb3JoinColumn extends Ejb3Column {
getMappingColumn() != null ? getMappingColumn().isNullable() : false,
referencedColumn.getSqlType(),
getMappingColumn() != null ? getMappingColumn().isUnique() : false,
+ null, // default-value
false
);
linkWithValue( value );
@@ -502,6 +504,7 @@ public class Ejb3JoinColumn extends Ejb3Column {
getMappingColumn().isNullable(),
column.getSqlType(),
getMappingColumn().isUnique(),
+ null, // default-value
false //We do copy no strategy here
);
linkWithValue( value );
Well, this is a hibernate-only solution.
You can't do this with the column annotation. I think the only way is to set the default value when a object is created. Maybe the default constructor would be the right place to do that.
This isn't possible in JPA.
Here's what you can do with the Column annotation: http://java.sun.com/javaee/5/docs/api/javax/persistence/Column.html
You can't do this with the column annotation. I think the only way is to set the default value when a object is created. Maybe the default constructor would be the right place to do that.
This isn't possible in JPA.
Here's what you can do with the Column annotation: http://java.sun.com/javaee/5/docs/api/javax/persistence/Column.html
JPA doesn't support that and it would be useful if it did. Using columnDefinition is DB-specific and not acceptable in many cases. setting a default in the class is not enough when you retrieve a record having null values (which typically happens when you re-run old DBUnit tests). What I do is this:
public class MyObject
{
int attrib = 0;
/** Default is 0 */
@Column ( nullable = true )
public int getAttrib()
/** Falls to default = 0 when null */
public void setAttrib ( Integer attrib ) {
this.attrib = attrib == null ? 0 : attrib;
}
}
Java auto-boxing helps a lot in that.
You can do the following:
@Column(name="price")
private double price = 0.0;
There! You've just used zero as the default value.
Note this will serve you if you're only accessing the database from this application. If other applications also use the database, then you should make this check from the database using Cameron's columnDefinition annotation attribute, or some other way.
@Column(columnDefinition="tinyint(1) default 1")
I just tested the issue. It works just fine. Thanks for the hint.
About the comments:
@Column(name="price")
private double price = 0.0;
This one doesn't set the default column value in the database (of course).
Seeing as I stumbled upon this from Google while trying to solve the very same problem, I'm just gonna throw in the solution I cooked up in case someone finds it useful.
From my point of view there's really only 1 solutions to this problem -- @PrePersist. If you do it in @PrePersist, you gotta check if the value's been set already though.
You can define the default value in the database designer, or when you create the table. For instance in SQL Server you can set the default vault of a Date field to (getDate()). Use insertable=false as mentioned in your column definition. JPA will not specify that column on inserts and the database will generate the value for you.
@PrePersist
void preInsert() {
if (this.dateOfConsent == null)
this.dateOfConsent = LocalDateTime.now();
if(this.consentExpiry==null)
this.consentExpiry = this.dateOfConsent.plusMonths(3);
}
In my case due to the field being LocalDateTime i used this, it is recommended due to vendor independence
Source: Stackoverflow.com