Author: danhaywood
Date: Mon May 26 10:31:43 2014
New Revision: 1597553
URL: http://svn.apache.org/r1597553
Log:
mapping blobs
Modified:
isis/site/trunk/content/components/objectstores/jdo/mapping-blobs.md
Modified: isis/site/trunk/content/components/objectstores/jdo/mapping-blobs.md
URL:
http://svn.apache.org/viewvc/isis/site/trunk/content/components/objectstores/jdo/mapping-blobs.md?rev=1597553&r1=1597552&r2=1597553&view=diff
==============================================================================
--- isis/site/trunk/content/components/objectstores/jdo/mapping-blobs.md
(original)
+++ isis/site/trunk/content/components/objectstores/jdo/mapping-blobs.md Mon
May 26 10:31:43 2014
@@ -6,13 +6,15 @@ Isis configures JDO/DataNucleus so that
As for [Joda dates](mapping-joda-dates.html), this requires the
`@javax.jdo.annotations.Persistent` annotation. However, whereas for dates one
would always expect this value to be retrieved eagerly, for blobs and clobs it
is not so clear cut.
+### Mapping Blobs
+
For example, in the `ToDoItem` class (of the [quickstart
archetype](../../../getting-started/quickstart-archetype.html)) the
`attachment` property (as of 1.5.0-snapshot) is as follows:
<pre>
@javax.jdo.annotations.Persistent(defaultFetchGroup="false", columns = {
@javax.jdo.annotations.Column(name = "attachment_name"),
@javax.jdo.annotations.Column(name = "attachment_mimetype"),
- @javax.jdo.annotations.Column(name = "attachment_bytes", sqlType =
"BLOB")
+ @javax.jdo.annotations.Column(name = "attachment_bytes",
jdbcType="BLOB", sqlType = "BLOB")
})
private Blob attachment;
@@ -33,7 +35,7 @@ If the `Blob` or `Clob` is mandatory, th
@javax.jdo.annotations.Persistent(defaultFetchGroup="false", columns = {
@javax.jdo.annotations.Column(name = "attachment_name",
allowsNull="false"),
@javax.jdo.annotations.Column(name = "attachment_mimetype",
allowsNull="false"),
- @javax.jdo.annotations.Column(name = "attachment_bytes", sqlType =
"BLOB", allowsNull="false")
+ @javax.jdo.annotations.Column(name = "attachment_bytes",
jdbcType="BLOB", sqlType = "BLOB", allowsNull="false")
})
private Blob attachment;
@@ -48,23 +50,47 @@ If the `Blob` or `Clob` is mandatory, th
> Instead of `@Mandatory`, using
> `@javax.jdo.annotations.Column(allowsNull="false")` will also work.
> However, as this last `@Column` annotation is only for Isis' benefit
> (DataNucleus ignores it in the presence of the `Persistent#columns`
> attribute) we prefer to use `@Mandatory` instead.
-Using the `@Column` annotation, you can also specify whether the `Blob` is
mapped to a `VARBINARY` rather than a `BLOB` column:
+
+### Mapping Clobs
+
+Mapping `Clob`s works in a very similar way, but the `@Column#sqlType`
attribute will be `CLOB`:
<pre>
- @javax.jdo.annotations.Column(name = "attachment_bytes", sqlType =
"VARBINARY", length=2048)
+ @javax.jdo.annotations.Persistent(defaultFetchGroup="false", columns = {
+ @javax.jdo.annotations.Column(name = "attachment_name"),
+ @javax.jdo.annotations.Column(name = "attachment_mimetype"),
+ @javax.jdo.annotations.Column(name = "attachment_chars", sqlType =
"CLOB")
+ })
+ private Clob doc;
+
+ @Mandatory
+ public Clob getDoc() {
+ return doc;
+ }
+ public void setDoc(final Clob doc) {
+ this.doc = doc;
+ }
+</pre>
+
+or `VARCHAR`:
+
+<pre>
+ @javax.jdo.annotations.Column(name = "attachment_chars", sqlType =
"VARCHAR", length=2048)
</pre>
-The maximum allowed length for a `VARBINARY` will vary by database vendor.
Obviously, only do this if you are sure that the data to be mapped fits into
the smaller size.
-Mapping `Clob`s works the exact same way, but the `@Column#sqlType` attribute
will either be `CLOB`
+# Mapping to VARBINARY or VARCHAR
+
+Instead of mapping to a `Blob` or `Clob` datatype, you might also specify map
to a `VARBINARY` or `VARCHAR`. In this case you will need to specify a length.
For example:
<pre>
- @javax.jdo.annotations.Column(name = "attachment_chars", sqlType =
"CLOB")
+ @javax.jdo.annotations.Column(name = "attachment_bytes", sqlType =
"VARBINARY", length=2048)
</pre>
-or `VARCHAR`,
+or
<pre>
@javax.jdo.annotations.Column(name = "attachment_chars", sqlType =
"VARCHAR", length=2048)
</pre>
+Support and maximum allowed length will vary by database vendor.
