How spring boot jpa criteria api is generated in JPQL

 

When we use entityManager.createQuery (query), we found that injection entityManager objects as follows:

 

 

 

It is: a proxy object of org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@40383b24. Also a FactoryBean.

Through this FactoryBean can create the actual proxy object:

// Determine current EntityManager: either the transactional one
            // managed by the factory or a temporary one for the given invocation.
            EntityManager target = EntityManagerFactoryUtils.doGetTransactionalEntityManager(
                    this.targetFactory, this.properties, this.synchronizedWithTransaction);

            if (method.getName().equals("getTargetEntityManager")) {
                // Handle EntityManagerProxy interface.
                if (target == null) {
                    throw new IllegalStateException("No transactional EntityManager available");
                }
                return target;
            }

 

 

 

 

The final call is org.hibernate.internal.SessionImpl # createQuery (javax.persistence.criteria.CriteriaQuery <T>)

@Override
    @SuppressWarnings("unchecked")
    public <T> QueryImplementor<T> createQuery(CriteriaQuery<T> criteriaQuery) {
        checkOpen();
        try {
            return (QueryImplementor<T>) criteriaCompiler().compile( (CompilableCriteria) criteriaQuery );
        }
        catch ( RuntimeException e ) {
            throw exceptionConverter.convert( e );
        }
    }

 

compile方法的最后，可以看到：

return criteria.interpret( renderingContext ).buildCompiledQuery(
                entityManager,
                new InterpretedParameterMetadata() {
                    @Override
                    public Map<ParameterExpression<?>, ExplicitParameterInfo<?>> explicitParameterInfoMap() {
                        return explicitParameterInfoMap;
                    }

                    @Override
                    public List<ImplicitParameterBinding> implicitParameterBindings() {
                        return implicitParameterBindings;
                    }
                }
        );

 

org.hibernate.query.criteria.internal.CriteriaQueryImpl#interpret方法代码如下：

    @Override
    public CriteriaInterpretation interpret(RenderingContext renderingContext) {
        final StringBuilder jpaqlBuffer = new StringBuilder();

        queryStructure.render( jpaqlBuffer, renderingContext );

        renderOrderByClause( renderingContext, jpaqlBuffer );

        final String jpaqlString = jpaqlBuffer.toString();

        log.debugf( "Rendered criteria query -> %s", jpaqlString );
。。。。

这里就看到了JPQL了。

继续找render方法：

public void render(StringBuilder jpaqlQuery, RenderingContext renderingContext) {
        renderSelectClause( jpaqlQuery, renderingContext );

        renderFromClause( jpaqlQuery, renderingContext );

        renderWhereClause( jpaqlQuery, renderingContext );

        renderGroupByClause( jpaqlQuery, renderingContext );
    }