DDevelopment & Design

Przekazywanie tablicy rekordów z Javy do procedury składowanej w Oracle’u

Poniżej znajduje się opis jak przekazywać string, tablicę stringów oraz tablicę par stringów z Javy do Oracle’a Należy utworzyć typy w bazie danych:

create or replace type VARCHAR2_PAIR as object( k varchar2(200), v varchar2(200));
create or replace type VARCHAR2_PAIRS_TABLE as table of VARCHAR2_PAIR;
create or replace type VARCHAR2_TABLE as table of VARCHAR2(200);

. Potem utworzyć procedurę składowaną

CREATE OR REPLACE PROCEDURE arrays_from_java(p_scalar varchar2
, p_array IN VARCHAR2_TABLE
, p_pairs_array in VARCHAR2_PAIRS_TABLE);

. A na końcu zawołać ją z Javy:

public static void callArrayProcedure() throws Exception{
    System.out.println("Preparing data");
    String[] list1=new String[2];
    list1[0] = "first string";
    list1[1] = "second string";

    String[][] list2=new String[2][];
    {
        String[] pair1 = new String[2];
        pair1[0] = "key1";
        pair1[1] = "value1";
        list2[0] = pair1;
    }
    {
        String[] pair2 = new String[2];
        pair2[0] = "key2";
        pair2[1] = "value2";
        list2[1] = pair2;
    }

    System.out.println("Preparing connection");
    SingleConnectionDataSource scds = new SingleConnectionDataSource();
    scds.setDriverClassName("oracle.jdbc.driver.OracleDriver");
    scds.setUrl("jdbc:oracle:thin:@host:1521:service_name");
    scds.setUsername(...);
    scds.setPassword(...);
    Connection conn = scds.getConnection();

    System.out.println("Preparing array of strings");
    ArrayDescriptor descriptor1 = ArrayDescriptor.createDescriptor("VARCHAR2_TABLE", conn );
    ARRAY arrayToPass1 = new ARRAY( descriptor1, conn, list1 );

    System.out.println("Preparing array of string pairs");
    ArrayDescriptor descriptor2 = ArrayDescriptor.createDescriptor("VARCHAR2_PAIRS_TABLE", conn );
    ARRAY arrayToPass2 = new ARRAY( descriptor2, conn, list2 );

    System.out.println("Calling procedure");
    OraclePreparedStatement ps = (OraclePreparedStatement) conn.prepareStatement( "{ call arrays_from_java( ?, ?, ? ) }" );
    ps.setString( 1, "string");
    ps.setARRAY( 2, arrayToPass1 );
    ps.setARRAY( 3, arrayToPass2 );
    ps.execute();
    ps.close();
}

.

Należy też dodać do classpath orai18n.jar, gdyż w przeciwnym wypadku jeśli baza nie będzie miała formatu UTF8 może występować błąd, że stringi się nullują podczas przekazywania do procedury

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DDevelopment & Design

Simple trick to DRY your Grails controller

Grails controllers are not very DRY. It's easy to find duplicated code fragments in default generated controller. Take a look at code sample below. It is duplicated four times in show, edit, update and delete actions:

class BookController {
def show() {
def bookInstance = Book.get(params.id)
if (!bookInstance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
return
        }
        [bookInstance: bookInstance]
    }
}

Why is it duplicated?

There is a reason for that duplication, though. If you move this snippet to a method, it can redirect to "list" action, but it can't prevent controller from further execution. After you call redirect, response status changes to 302, but after method exits, controller still runs subsequent code.

Solution

At TouK we've implemented a simple trick to resolve that situation:

  1. wrap everything with a simple withStoppingOnRender method,
  2. whenever you want to render or redirect AND stop controller execution - throw EndRenderingException.

We call it Big Return - return from a method and return from a controller at once. Here is how it works:

class BookController {
def show(Long id) {
withStoppingOnRender {
Book bookInstance = Book.get(id)
validateInstanceExists(bookInstance)
            [bookInstance: bookInstance]
        }
    }

protected Object withStoppingOnRender(Closure closure) {
try {
return closure.call()
        } catch (EndRenderingException e) {}
    }

private void validateInstanceExists(Book instance) {
if (!instance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
throw new EndRenderingException()
        }
    }
}

class EndRenderingException extends RuntimeException {}

Example usage

For simple CRUD controllers, you can use this solution and create some BaseController class for your controllers. We use withStoppingOnRender in every controller so code doesn't look like a spaghetti, we follow DRY principle and code is self-documented. Win-win-win! Here is a more complex example:

class DealerController {
@Transactional
def update() {
withStoppingOnRender {
Dealer dealerInstance = Dealer.get(params.id)
validateInstanceExists(dealerInstance)
validateAccountInExternalService(dealerInstance)
checkIfInstanceWasConcurrentlyModified(dealerInstance, params.version)
            dealerInstance.properties = params
saveUpdatedInstance(dealerInstance)
redirectToAfterUpdate(dealerInstance)
        }
    }
}