Call a java method to generate SQL query in myBatis

Question

I am using myBatis to write some SQL queries, the problem is that I have tables that have several columns ( around 50 column). So writing the insert query like this :

<insert id="insert" parameterType="com.atos.tables.Table1>
  insert into ot ( id, c1, c2, ....,c50) values (#{id}, #{c1},#{c2},... #{c50})
</insert>

is very tedious.

I can create a method in java that generate the String of the queries automatically, but how can I call this method from the mapper.xml ?

And if I use myBatis annotations I cannot call a method in an interface. I don't know if I am missing something, is there a way to do this??

Thanks for helping.

Bogdan · Accepted Answer · 2014-05-24 16:35:53Z

1

There isn't any way I'm aware of for doing this directly.

What you could try is to generate the columns at compile or deploy time in a separate file as <sql> elements and then include them in your mapper files as needed.

There is also this statement-builders feature added to MyBatis that alows you to build SQL from code so maybe have a look at that also.

answered May 24, 2014 at 16:35

Bogdan

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Roman-Stop RU aggression in UA · Accepted Answer · 2014-06-04 11:23:24Z

1

The main problem is not in query string generation: this can be done easily using scripting support for example with mybatis-velocity.

The main problem is to set parameters dynamically. This can done in mybatis-velocity by defining custom directive which will dynamically create org.apache.ibatis.mapping.ParameterMapping.

It may be used in mapper like this:

<insert id="insert">
   insert into ot (
     #field_names('com.atos.tables.Table1')
   ) values ( @{id},
     #params_for_fields('com.atos.tables.Table1')
   )
</insert>

Here #field_names adn #params_for_fields is a custom directives which you need to implement. field_names should iterate over fields of class which is passed as argument and generate comma separated list of field.

params_for_fields should create new parameters mapping and add them to list of parameters mappings maintained by velocity language driver.

You may look to built-in repeat directive and ParameterMappingCollector to see how parameter mappings can be created and accessed.

edited Jun 4, 2014 at 11:23

answered May 29, 2014 at 20:38

Roman-Stop RU aggression in UA

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2 Comments

Mouna Over a year ago

The problem with this solution is that my fields have complex name (is not c1 , c2.. I used these names only to simplify), In the method of generation of the query I get the fields from the class and I generate the query.

Roman-Stop RU aggression in UA Over a year ago

This is not a problem. You can shape custom directives so you can create directives which iterates over the fields of a class. I've updated the answer.

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