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.

Usage

To use SProcWrapper, add the following lines to your pom.xml:

xml

<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>zalando-sprocwrapper</artifactId>
    <version>${zalando-sprocwrapper.version}</version>
</dependency>

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:

java

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

sql
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:

java

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

sql
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.

Configure global value transformer loader

Global value transformer loader loads global value transformers from the classpath. By default, it searches value
transformers in org.zalando package. You can change this behaviour using
the global.value.transformer.search.namespace environment variable:

shell
EXPORT global.value.transformer.search.namespace="my.package"

or by calling a method:

java
GlobalValueTransformerLoader.changeNamespaceToScan("my.package");

It is also possible to provide multiple scan packages using ; separator:

shell
EXPORT global.value.transformer.search.namespace="my.package;another.package;third.package"

Prerequisites

Java 17
To compile, one should use Maven 3.0.0 or above

Dependencies

Spring Framework 5.x
PostgreSQL JDBC driver ;)
Google Guava

See pom.xml for the full list of dependencies.

How to run integration tests

The provided helper script will start a PostgreSQL instance with Docker on port 5432 and run integration tests:

shell
./test.sh

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:

🚨 Upgrading from 2.x to 3.x? Please be aware that default scanning package for custom objectTransformer has changed from de.zalando to org.zalando.