jdbc api c library

#include <string.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include "jni.h"
#include "jdbcapi.h"

struct jdbc_api_impl
{
    JDBC_API base;
    JNIEnv *env;
    jclass cls;
    JavaVMOption options[ 1 ];
    JavaVMInitArgs vm_args;
    JavaVM *jvm;
    jmethodID mid_get_connection;
    jmethodID mid_execute;
    jmethodID mid_prepare_stmt;
    jmethodID mid_execute_query;
    jmethodID mid_set_column;
    jmethodID mid_read_value;
    jmethodID mid_log_off;

};
typedef struct jdbc_api_impl JDBC_API_IMPL;

static double read_value ( JDBC_API *obj,  int index_stmt)
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jint status;
    jint res;
    jdouble value;

    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return -1;
    }
    value = ( *api_impl->env )->CallStaticDoubleMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_read_value,
        index_stmt
        );
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    return value;

}

static bool get_connection (
    JDBC_API * obj,
    const char* ul,
    const char* userid,
    const char* pwd )
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jboolean jflag;
    jint status;
    jint res;

    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return -1;
    }
    jstring url = ( *api_impl->env )->NewStringUTF( api_impl->env, ul );
    jstring user = ( *api_impl->env )->NewStringUTF( api_impl->env, userid );
    jstring passwd = ( *api_impl->env )->NewStringUTF( api_impl->env, pwd );

    jflag = ( *api_impl->env )->CallStaticBooleanMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_get_connection,
        url,
        user,
        passwd );
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, url, 0 );
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, user, 0 );
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, passwd, 0 );
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    return jflag;
}

static int prepare_stmt ( JDBC_API * obj, const char *sql )
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jboolean jflag;
    jint res;
    jint index;
    jint status;

    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return false;
    }

    jstring query = ( *api_impl->env )->NewStringUTF( api_impl->env, sql );
    index = ( *api_impl->env )->CallStaticIntMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_prepare_stmt,
        query );
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, query, 0 );
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    return index;

}

static void set_column ( JDBC_API * obj, int id, const char *col_name )
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jint res;
    jint status;

#if 0
    status = ( *api_impl->jvm )->GetEnv(
        api_impl->jvm,
        (void**) &api_impl->env,
        api_impl->vm_args.version );
    if ( status != JNI_OK )
    {
        res = ( *api_impl->jvm )->AttachCurrentThread(
            api_impl->jvm,
            (void**) &api_impl->env,
            NULL );
        if ( res < 0 )
        {
            perror( "Attach the ENV failed\n" );
            return;
        }
        //const char* col_name = (char *) POINT_COLUMN( point_array[ j ] );
        jstring colname = ( *api_impl->env )->NewStringUTF(
            api_impl->env,
            col_name );
        printf( "set_column :%s\n", col_name );
        ( *api_impl->env )->CallStaticVoidMethod(
            api_impl->env,
            api_impl->cls,
            api_impl->mid_set_column,
            id,
            colname );
        ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, colname, 0 );
        ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    }
    else
    {
#endif
    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return;
    }
    jstring colname = ( *api_impl->env )->NewStringUTF(
        api_impl->env,
        col_name );
    printf( "set_column :%s\n", col_name );
    ( *api_impl->env )->CallStaticVoidMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_set_column,
        id,
        colname );
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, colname, 0 );
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );
 //}

}

static bool execute_query ( JDBC_API * obj ,int index_stmt)
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jboolean jflag;
    jint res;
    jint status;

    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return false;
    }

    jflag = ( *api_impl->env )->CallStaticBooleanMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_execute_query ,
        index_stmt);
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    return jflag;

}
static bool execute (JDBC_API* obj, const char* sql)
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jboolean jflag;
    jint res;
    jint status;

    res = ( *api_impl->jvm )->AttachCurrentThread(
            api_impl->jvm,
            (void**) &api_impl->env,
            NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return false;
    }
    jstring query = ( *api_impl->env )->NewStringUTF( api_impl->env, sql );
    jflag = ( *api_impl->env )->CallStaticBooleanMethod(
            api_impl->env,
            api_impl->cls,
            api_impl->mid_execute,
            query);
    ( *api_impl->env )->ReleaseStringUTFChars( api_impl->env, query, 0 );
    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

    return jflag;
}

static void logoff ( JDBC_API * obj )
{
    JDBC_API_IMPL * api_impl = (JDBC_API_IMPL*) obj;
    jint res;
    jint status;

    res = ( *api_impl->jvm )->AttachCurrentThread(
        api_impl->jvm,
        (void**) &api_impl->env,
        NULL );
    if ( res < 0 )
    {
        perror( "Attach the ENV failed\n" );
        return;
    }
    ( *api_impl->env )->CallStaticVoidMethod(
        api_impl->env,
        api_impl->cls,
        api_impl->mid_log_off );

    ( *api_impl->jvm )->DetachCurrentThread( api_impl->jvm );

}

JDBC_API* jdbcapi_create ()
{
    long status;
    JDBC_API_IMPL * api_impl = malloc( sizeof(JDBC_API_IMPL) );

    api_impl->options[ 0 ].optionString = "-Djava.class.path=.:/home/pakkio/spazio251.working/spazio/java/spfab/externalLibraries/com/h2database/h2/1.3.163/h2-1.3.163.jar";
    memset( &api_impl->vm_args, 0, sizeof( api_impl->vm_args ) );
    api_impl->vm_args.version = JNI_VERSION_1_6;
    api_impl->vm_args.nOptions = 1;
    api_impl->vm_args.options = api_impl->options;

    status = JNI_CreateJavaVM(
        &api_impl->jvm,
        (void**) &api_impl->env,
        &api_impl->vm_args );
    if ( status != JNI_OK )
    {
        perror( "JVM Created failed!\n" );
        return NULL;
    }
    else
    {
        printf( "JVM Created success!\n" );
        api_impl->cls = ( *api_impl->env )->FindClass(
            api_impl->env,
            "DevJDBC" );
        if ( api_impl->cls != 0 )
        {
            api_impl->mid_get_connection =
                ( *api_impl->env )->GetStaticMethodID(
                    api_impl->env,
                    api_impl->cls,
                    "getConnection",
                    "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Z" );

            api_impl->mid_prepare_stmt = ( *api_impl->env )->GetStaticMethodID(
                api_impl->env,
                api_impl->cls,
                "prepareStmt",
                "(Ljava/lang/String;)I" );

            api_impl->mid_set_column = ( *api_impl->env )->GetStaticMethodID(
                api_impl->env,
                api_impl->cls,
                "setColname",
                "(ILjava/lang/String;)V" );

            api_impl->mid_execute = ( *api_impl->env )->GetStaticMethodID(
                    api_impl->env,
                    api_impl->cls,
                    "execute",
                    "(Ljava/lang/String;)Z" );

            api_impl->mid_execute_query = ( *api_impl->env )->GetStaticMethodID(
                api_impl->env,
                api_impl->cls,
                "executeQuery",
                "(I)Z" );
            api_impl->mid_read_value = ( *api_impl->env )->GetStaticMethodID(
                api_impl->env,
                api_impl->cls,
                "readValue",
                "(I)D" );
            api_impl->mid_log_off = ( *api_impl->env )->GetStaticMethodID(
                api_impl->env,
                api_impl->cls,
                "logoff",
                "()V" );
            api_impl->base.get_connection = get_connection;
            api_impl->base.prepare_stmt = prepare_stmt;
            api_impl->base.set_column = set_column;
            api_impl->base.execute = execute;
            api_impl->base.execute_query = execute_query;
            api_impl->base.read_value = read_value;
            api_impl->base.logoff = logoff;
        }
        else
        {
            perror( "can not find the JDBC class\n" );
            return NULL;
        }
    }
    return (JDBC_API *) api_impl;
}

void jdbcapi_destroy ( JDBC_API * api_obj )
{
    //JDBC_API_IMPL* api_impl = (JDBC_API_IMPL *) api_obj;
    printf( "DevJDBC:%s\n", __func__ );
    if ( api_obj  != NULL )
    {
        free( api_obj );
    }

}