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I am using Mybatis with the spring boot application. Where I used to generate MySql query using ProviderMethodResolver. My application supports mybatis annotation processor and XML processor.

To achieve that I used this Mybatis configuration:

In appication.properties file

mybatis.mapper-locations=classpath*:/repository/**/*Repository.xml

and a MybatisConfiguration.java

@Configuration
@EnableTransactionManagement
public class MybatisConfiguration {

    @Bean
    ConfigurationCustomizer mybatisConfigurationCustomizer() {
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true);
                configuration.setCacheEnabled(true);
            }
        };
    }
}

With above configuration, everything(@Select, @Insert, @ResultMap) seems working fine except implementation of @SelectProvider.

SelectProvider Implemetation is

VariantRepository.java

@Mapper
public interface VariantRepository {

    @SelectProvider(type = VariantSqlProvider.class, method = "getProductAttribute")
    VariantDto findByProductAttribute(@Param("productAttributeDto") ProductAttributeDto productAttributeDto);
}

I am using org.apache.ibatis.annotations.Param

ProductAttributeDto.java

@Data
public class ProductAttributeDto {

    private Integer productId;

    Map<String, String> attributes;
}

VariantSqlProvider.class

  public class VariantSqlProvider implements ProviderMethodResolver {

    @SuppressWarnings("unused")
    public static String getProductAttribute(final ProductAttributeDto productAttributeDto) {
        return new SQL() {{
            SELECT("*");
            FROM("ec_product_variant AS pv");
            if (Objects.nonNull(productAttributeDto.getAttributes())) {
                for (Entry<String, String> entry : productAttributeDto.getAttributes().entrySet()) {
                    if(Objects.nonNull(entry.getValue())) {
                        INNER_JOIN(
                                new StringBuilder("ec_attributes AS ")
                                .append(entry.getKey())
                                .append(" ON ")
                                .append(entry.getKey()).append(".id = pv.").append(entry.getKey())
                                .append(" AND ")
                                .append(entry.getKey()).append(".value=#{productAttributeDto.attributes.").append(entry.getKey())
                                .append("}").toString()
                        );
                    } else {
                        WHERE("pv." + entry.getKey() + " IS NULL");
                    }
                }
            }
            if(Objects.nonNull(productAttributeDto.getProductId())) {
                WHERE("pv.product_id = #{productAttributeDto.productId}");
            }
        }}.toString();
    }
}

When I invoke the findByProductAttribute method, I get an error like this

org.apache.juli.logging.DirectJDKLog: Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.builder.BuilderException: Error invoking SqlProvider method 'public static java.lang.String com.ecommerce.app.repository.product.sqlprovider.VariantSqlProvider.getProductAttribute(com.ecommerce.app.model.product.ProductAttributeDto)' with specify parameter 'class org.apache.ibatis.binding.MapperMethod$ParamMap'.  Cause: org.apache.ibatis.binding.BindingException: Parameter 'arg0' not found. Available parameters are [productAttributeDto, param1]] with root cause
org.apache.ibatis.binding.BindingException: Parameter 'arg0' not found. Available parameters are [productAttributeDto, param1]
        at org.apache.ibatis.binding.MapperMethod$ParamMap.get(MapperMethod.java:212)
        at org.apache.ibatis.builder.annotation.ProviderSqlSource.extractProviderMethodArguments(ProviderSqlSource.java:223)

The SQL query I am expecting to generate is:

SELECT *
FROM ec_product_variant AS pv 
INNER JOIN ec_attributes AS color ON color.id = pv.color AND color.value=? 
WHERE (pv.size IS NULL AND pv.product_id = ?)

The query is based on the attributes key-value pair in productAttributeDto

Here mybatis is looking for arg0 instead of productAttributeDto. Can anyone help on this. What am I doing wrong here? Thanks in advance.

Anu
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    Try adding `@Param` to the provider method as well i.e. `public static String getProductAttribute(@Param("productAttributeDto") final ProductAttributeDto productAttributeDto) {`. – ave Aug 16 '20 at 02:01
  • @ave This helped. Could you explain this and create a answer for future reference. – Anu Aug 16 '20 at 08:08

1 Answers1

3

The error is caused by the parameter name mismatch between the mapper method and the provider method.

  • The param name of the mapper method is specified by @Param annotation i.e. productAttributeDto.
  • The param name is not specified in the provider method, so the default name arg0 is used.

These names must match.

There are two solutions.

  1. Add @Param annotation on the provider method parameter.
  2. Build your application with -parameters compiler option enabled.

The solution 1 is pretty straightforward.

public static String getProductAttribute(
  @Param("productAttributeDto") final ProductAttributeDto productAttributeDto) {

The solution 2 depends on how you build your application.

If you use Maven, you may need to configure maven-compiler-plugin in the pom.xml. e.g.

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <configuration>
        <compilerArgs>
          <arg>-parameters</arg>
        </compilerArgs>
      </configuration>
    </plugin>

When using IDE, you might need to configure the build setting.

This way, MyBatis can retrieve the parameter name from the method signature, so you don't need to use @Param annotation (you can still use @Param if you want, though).

As a result, the mapper method can be simpler...

@SelectProvider(type = VariantSqlProvider.class, method = "getProductAttribute")
VariantDto findByProductAttribute(ProductAttributeDto productAttributeDto);

...and the provider method in your question should work as-is.

ave
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