Fetching a blob from database as a byte[] using myBatis

Question

I am using spring MyBatis 1.2.0 in a project, where I have a query that gets data from a BLOB field in an Oracle 11g database. I want to retrieve the field as a byte array (byte[]), my Code is:

<select id="getResponse" resultType="_byte[]" parameterType="string">
   select blob_Data from Table where id = #{value,jdbcType=VARCHAR} AND ROWNUM = 1    
</select>

This is giving following error:

java.lang.ClassCastException: [B incompatible with [Ljava.lang.Object;
    at org.apache.ibatis.binding.MapperMethod.convertToArray(MapperMethod.java:136)
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:58)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:43)

Apart from this, I have also tried using resultMap:

<resultMap id="responseMap" type="ResponseMessageModel">
    <result property="blobData" column="blob_Data"/>
</resultMap>

<select id="getResponse" resultMap="responseMap" parameterType="string">
   select blob_Data from table where id = #{value,jdbcType=VARCHAR} AND ROWNUM = 1    
</select>

and also specifying the javaType:

<resultMap id="responseMap" type="ResponseMessageModel">
      <result property="blobData" javaType="_byte[]" column="blob_Data"/>
</resultMap>

<select id="getResponse" resultMap="responseMap" parameterType="string">
   select blob_Data from table where id = #{value,jdbcType=VARCHAR} AND ROWNUM = 1    
</select>

but with no luck, all give the same ClassCastException

Could someone please tell me what I am doing wrong?

Community · Accepted Answer · 2017-05-23 12:25:52Z

4

Try to specify a JDBC type in your result map:

<result property="blobData" column="blob_Data" jdbcType="BLOB"/>

Here an example from Camunda BPM:

Mapping with result map "resourceResultMap", that contains a bytes property

Entity with bytes (byte[]) field

Edit:

If it is not working, please have a look at following question. It suggests to use BINARY as JDBC type or to use a custom type handler like in the accepted answer.

edited May 23, 2017 at 12:25

CommunityBot

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answered Feb 23, 2015 at 9:23

gclaussn

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1 Comment

Sumit Over a year ago

I tried this but now I am getting a null from the database, but the BLOB column contains some value.

Sumit · Accepted Answer · 2015-09-25 19:52:54Z

2

So, I got this to work by making the following changes in my code-

I am using a resultMap and specified both javaType and jdbcType:

<resultMap id="responseMap" type="ResponseMessageModel">
      <result property="blobData" javaType="_byte[]" column="blob_Data" jdbcType="BLOB"/>
</resultMap>

<select id="getResponse" resultMap="responseMap" parameterType="string">
   select blob_Data from table where id = #{value,jdbcType=VARCHAR} AND ROWNUM = 1    
</select>

By doing this, I am able to successfully retrieve the BLOB value as a byte[].

answered Sep 25, 2015 at 19:52

Sumit

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Comments

Sumit · Accepted Answer · 2019-10-11 08:01:33Z

0

I have used this in my query to fetch the blob column value as a string

UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(BLOB_COLUMN_NAME, 200,1)) FAX_NOTES

This maps the blob to a string and mybatis has:

<result column="FAX_NOTES" property="faxNotes"  jdbcType="BLOB" />

In the java class -

private String faxNotes;

edited Oct 11, 2019 at 8:01

Sumit

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answered Oct 9, 2019 at 15:09

BPeela

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