SProcWrapper

Library to make PostgreSQL stored procedures(SProcs) available through simple Java "SProcService" interfaces including automatic object serialization and deserialization (using typemapper and convention-over-configuration).

Supports horizontal database sharding (partition/access logic lies within application), easy use of pg_advisory_lock through annotations to ensure single Java node execution, configurable statement timeouts per stored procedure, and PostgreSQL types including enums and hstore.

Type Mapping

SprocWrapper provides an efficient and easy-to-use mechanism for translating values from database to Java objects and vice-versa. It allows us to map not only primitive types, but also complex types (Java domain objects).

Here are some examples!

Using basic types:

@SProcService
public interface CustomerSProcService {
  @SProcCall
  int registerCustomer(@SProcParam String name, @SProcParam String email);
}

CREATE FUNCTION register_customer(p_name text, p_email text)
RETURNS int AS
$$
  INSERT INTO z_data.customer(c_name, c_email)
       VALUES (p_name, p_email)
    RETURNING c_id
$$
LANGUAGE 'sql' SECURITY DEFINER;

And a complex type:

@SProcService
public interface OrderSProcService {
  @SProcCall
  List<Order> findOrders(@SProcParam String email);
}

CREATE FUNCTION find_orders(p_email text,
  OUT order_id int,
  OUT order_date timestamp,
  OUT shipping_address order_address)
RETURNS SETOF RECORD AS
$$
  SELECT o_id,
         o_date,
         ROW(oa_street, oa_city, oa_country)::order_address
    FROM z_data.order
    JOIN z_data.order_address
      ON oa_order_id = o_id
    JOIN z_data.customer
      ON c_id = o_customer_id
   WHERE c_email = p_email
$$
LANGUAGE 'sql' SECURITY DEFINER;

Please check unit/integration tests for more examples.

The following table shows the mapping between a database type and a Java type:

Database	Java Type
smallint	int
integer	int
bigint	long
decimal	java.math.BigDecimal
numeric	java.math.BigDecimal
real	float
double precision	double
serial	int
bigserial	long
varchar	java.lang.String
char	char
text	java.lang.String
timestamp	java.sql.Timestamp
timestamptz	java.sql.Timestamp
date	java.sql.Timestamp
time	java.sql.Timestamp
timetz	java.sql.Timestamp
boolean	boolean
enum	java.lang.Enum
array	java.util.List / java.util.Set
hstore	java.util.Map<java.lang.String, java.lang.String>

Note: Sprocwrapper doesn't support functions returning arrays as a single output. If one wants to return a collection, please return a SETOF instead.

Prerequisites

• Java 7
• To compile, one should use Maven 2.1.0 or above

Dependencies

• Spring Framework
• PostgreSQL JDBC driver ;)
• Google Guava
• and more see pom.xml for details

How to run integration tests

• install local PostgreSQL cluster running on 5432
• allow connection with postgres/postgres or create a new user and set config values in pom.xml and application.test.properties

• create schema and database privileges required for test cases

• make sure you have hstore extension installed, preferably in template1
• create zalando_test database on your localhost PostgreSQL cluster

• possibly add hstore extension to database

• run integration tests (JUnit tests with database access): mvn clean test -Pintegration-test

Known issues

• PostgreSQL JDBC driver does not honor identical type names in different schemas, this may lead to issues if typemapper is used where types are present with equal name in more than one schema (this problem is solved now with the commit 3ca94e64d6322fa91c477200bfb3719deaeac153 to pgjdbc driver);
• PostgreSQL domains are not supported as for now;
• PostgreSQL hstore type is mapped from and to Map<String,String>, there is no way to use Map of different types for now;
• Two different datasources with the same JDBC URL and different search paths might not work properly when we have types with the identical name;
• SprocWrapper relies on the search path to resolve conflicting types with the same name (right now, we are not checking the schema). If one specifies the schema of the stored procedure's return type, SprocWrapper might end up using the wrong one, because it will use the search_path to resolve the conflict. For more info check test: SimpleIT.testTypeLookupBugWithSchema;
• For integration with Spring's transaction management use the TransactionAwareDataSourceProxy as the data source injected into the data source provider.

Documentation

You can find some more information about the SProcWrapper in our various Zalando Technology blog posts:

• http://tech.zalando.com/goto-2013-why-zalando-trusts-in-postgresql/
• http://tech.zalando.com/zalando-stored-procedure-wrapper-part-i/
• http://tech.zalando.com/files/2013/04/jug_dortmund_april_2013.pdf

License

Copyright 2012-2013 Zalando GmbH

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.