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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I used to code in Java before I met groovy. Like most of you, groovy attracted me with many enhancements. This was to my surprise to discover that method visibility in groovy is handled different than Java!

Consider this example:

class Person {
private String name
public String surname

private Person() {}

private String signature() { "${name?.substring(0, 1)}. $surname" }

public String toString() { "I am $name $surname" }
}

How is this class interpreted with Java?

  1. Person has private constructor that cannot be accessed
  2. Field "name" is private and cannot be accessed
  3. Method signature() is private and cannot be accessed

Let's see how groovy interpretes Person:

public static void main(String[] args) {
def person = new Person() // constructor is private - compilation error in Java
println(person.toString())

person.@name = 'Mike' // access name field directly - compilation error in Java
println(person.toString())

person.name = 'John' // there is a setter generated by groovy
println(person.toString())

person.@surname = 'Foo' // access surname field directly
println(person.toString())

person.surname = 'Bar' // access auto-generated setter
println(person.toString())

println(person.signature()) // call private method - compilation error in Java
}

I was really astonished by its output:

I am null null
I am Mike null
I am John null
I am John Foo
I am John Bar
J. Bar

As you can see, groovy does not follow visibility directives at all! It treats them as non-existing. Code compiles and executes fine. It's contrary to Java. In Java this code has several errors, pointed out in comments.

I've searched a bit on this topic and it seems that this behaviour is known since version 1.1 and there is a bug report on that: http://jira.codehaus.org/browse/GROOVY-1875. It is not resolved even with groovy 2 release. As Tim Yates mentioned in this Stackoverflow question: "It's not clear if it is a bug or by design". Groovy treats visibility keywords as a hint for a programmer.

I need to keep that lesson in mind next time I want to make some field or method private!

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