Solving java.io.FileNotFoundException in Spring and iBATIS

I'm happily hacking about with iBATIS Spring DAO classes. I exposed the DAO classes using RPC services with GWT and the GWT server library and I run these RPC services in Tomcat. I also wanted to have unit tests that test my DAO classes, and there is this wonderful thing called gienah-testing on Google code, that allowed me to use Spring to inject the DAO classes into my unit test classes.

Now at this stage I started to get a FileNotFoundException on either my Spring configuration files or my SqlMapConfig.xml. When I referred to the configuration files using the scheme "/com/acme/config.xml", this caused loading the SqlMapConfig configuration to fail when running in Tomcat. I could solve the problem in Tomcat by referring to "WEB-INF/classes/com/acme/config.xml", but this caused my gienah-testing unit test classes to fail with a FileNotFoundException on the Spring configuration.

To solve this problem, I had to make sure that everything was loaded from the classpath using the ClassPathXmlApplicationContext. This is very simple, just prefix the location of the configuration file with "classpath:" without the quotes, e.g. "classpath:/com/acme/config.xml". This way both the gienah-test unit tests will load the configuration from the classpath using the classloader (e.g. in /classes if that were to be your output folder in Eclipse) and the web container will also load the configuration from the classpath using the classloader (in this case WEB-INF/classes). Here is a snippet of the gienah-testing test class, where data.xml is the configuration file containing the iBATIS Spring DAO configuration:

@RunWith(value = SpringRunner.class)
@Configuration(locations = {"classpath:/com/acme/data/data.xml", 
"classpath:/com/acme/test/test.xml"})
public class AcmeTest {

All other configuration files also refer to any underlying configuration files using the "classpath:" prefix, again in order to make sure that the ClassPathXmlApplicationContext is used. This is a snippet from the web.xml, injecting data.xml into the application context configuration file location:

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:/com/acme/data/data.xml</param-value>
</context-param>

The data.xml containing the iBATIS Spring DAO configuration injects the SqlMapConfig.xml, also with the "classpath:" prefix, as shown in the snippet below:

<bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
    <property name="dataSource" ref="myDataSource" />
    <property name="configLocation" value="classpath:/com/acme/data/SqlMapConfig.xml" />
</bean>

This should solve any FileNotFoundException problems in both the gienah-testing unit tests and when running in Tomcat. It works like a charm for me :-)

Mapping PostgreSQL Arrays with iBATIS

I needed to map a PostgreSQL integer array column to a Java integer array using iBATIS. The following is what seems to do the trick. Suppose you have a table with an integer array:

create my_table (
  id integer primary key,
  array_column integer[]
);

And some data was inserted using e.g. the following insert statement:

insert into my_table (id, array_column) values (1, array[1, 2, 3]);

Now lets have a Java class that can map to the above table, as follows:

public class MyTable {

  private int id = 0;
  private int[] arrayColumn = null;
  
  public int getId() { return id; }
  public void setId(int id) { this.id = id; }
  public int[] getArrayColumn() { return arrayColumn; }
  public void setArrayColumn(int[] arrayColumn)
    { this.arrayColumn = arrayColumn; }
  
}

We will now specify a select map, and we pass a result map to the select which is going to contain the mappings from the various columns to the properties in the Java bean.

<select id="getMyTable" parameterClass="int" resultClass="MyTable"
        resultMap="myTableResult">
    select id, array_column from my_table where id = #id#
</select>

The result map that we refer to in the resultMap attribute in the above select map is specified below:

<resultMap id="myTableResult" class="MyTable">
    <result property="id" column="id" />
    <result property="arrayColumn" column="array_column" jdbcType="ARRAY"
            javaType="java.sql.Array" typeHandler="ArrayTypeMapper" />
</resultMap>

In this result map, we map the id column to the id property and the array_column column to the arrayColumn property. There is however additional configuration needed for this second mapping. We specify that the JDBC type is ARRAY (as in java.sql.Types.ARRAY). We also specify that the Java type is java.sql.Array, but more importantly we specify the typeHandler attribute, which refers to the handler that is going to handle this array, and it is called ArrayTypeMapper. It implements TypeHandlerCallback, and its contents are as follows:

import java.sql.Array;
import java.sql.SQLException;

import com.ibatis.sqlmap.client.extensions.ParameterSetter;
import com.ibatis.sqlmap.client.extensions.ResultGetter;
import com.ibatis.sqlmap.client.extensions.TypeHandlerCallback;

public class ArrayTypeMapper implements TypeHandlerCallback {

  public void setParameter(ParameterSetter setter, Object parameter) 
        throws SQLException {
    throw new UnsupportedOperationException("Not implemented");
  }

  public Object getResult(ResultGetter getter) throws SQLException {
    Array array = getter.getResultSet().getArray(getter.getColumnName());
    if (!getter.getResultSet().wasNull()) {
      return array.getArray();
    } else {
      return null;
    }
  }

  public Object valueOf(String s) {
    throw new UnsupportedOperationException("Not implemented");
  }
}

It is very convenient that the getter object has the column name available (so we can avoid having to explicitely name the column or use indexes). Do not get the array from the array object immediately, you should first check whether is was null. If that was the case, return null (causing the MyTable object's array to be set to null), otherwise return array.getArray(). This will automatically cause the int[] in MyTable to be filled with the contents of the array column of my_table.