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Getting Started with ASN.1 Java Compiler

The best way of learning any language or notation is to read some examples of it. In this tutorial, we will walk you through creating and running a simple ASN.1 application. For more details, please see the ASN.1 Java Compiler User's Guide.

Installing the ASN.1 Java Compiler

Click here for instructions on how to download and install the ASN.1 SDK and ASN.1 Java Compiler plugin.

Setting up the License

Request a trial license or purchase a permanent license from ASN Lab website. In Eclipse click Windows (on Mac, Eclipse) > Preferences > ASN.1 > ASN.1 Java Compiler to open the ASN.1 Java Compiler preference page, enter the serial number of license in the General section and click OK.

The MyHTTP Example

The MyHTTP example is adapted from https://www.w3.org/Protocols/HTTP-NG/asn1.html, it's a simplified form of the GET request from FHTTP. For our example, suppose that we need to employ the ASN.1 module as we have seen in the ASN.1 Development Tools getting started tutorial.

  1. Select File > New > Project...
  2. Under ASN.1 category, select ASN.1 Project, then click Next.
  3. For project name, enter 'MyHTTP' and click Finish.
  4. ASN.1 files may now be added to the project by copying to the source folder, or creating ASN.1 files from scratch by
  5. Select File > New > Other...
  6. Under the ASN.1 category, select ASN.1 Module, then click Next.
  7. For module name, enter 'MyHTTP' and click Finish.
  8. Enter the following content in the opening editor:
    MyHTTP DEFINITIONS
    AUTOMATIC TAGS ::=
    BEGIN
    
       GetRequest ::= SEQUENCE {
          header-only   BOOLEAN,
          lock          BOOLEAN,
          accept-types  AcceptTypes,
          url           Url,
          ...,
          timestamp     GeneralizedTime
       }
    
       AcceptTypes ::= SET {
          standards   BIT STRING { html(0), plain-text(1), gif(2), jpeg(3) } (SIZE(4)) OPTIONAL,
          others      SEQUENCE OF VisibleString (SIZE(4)) OPTIONAL
       }
    
       Url ::= VisibleString (FROM("a".."z"|"A".."Z"|"0".."9"|"./-_~%#"))
    
       myRequest GetRequest ::= {
          header-only  TRUE,
          lock         FALSE,
          accept-types {
             standards { html, plain-text }
          },
          url          "www.asnlab.org",
          timestamp    "20121221121221Z"
       }
    
    END
  9. Save the ASN.1 file, then the compiled Java classes files will be automatically generated (If not, please set up license).
  10. Create a Java project test, and add the ASN.1 Java Runtime to the build path.
  11. Copy the generated Java class files into proper package ("MyHTTP" in this case) folder in the project.
  12. Create a TestMyHttp.java file in the project with the following contents:
    import java.io.ByteArrayOutputStream;
    import java.util.Calendar;
    
    import MyHTTP.AcceptTypes;
    import MyHTTP.GetRequest;
    import MyHTTP.Standards;
    
    
    public class TestMyHttp {
    
       public static void main(String[] args) throws Exception {
          GetRequest getRequest=new GetRequest();
          getRequest.header_only=true;
          getRequest.lock=false;
          getRequest.accept_types=new AcceptTypes();
          getRequest.accept_types.standards=new Standards(new byte[1],(byte)4);
          getRequest.accept_types.standards.setHtml();
          getRequest.accept_types.standards.setPlain_text();
          getRequest.url="www.asnlab.org";
          Calendar cal = Calendar.getInstance();
          cal.set(Calendar.YEAR, 2012);
          cal.set(Calendar.MONTH, Calendar.DECEMBER);
          cal.set(Calendar.DAY_OF_MONTH, 21);
          cal.set(Calendar.HOUR_OF_DAY, 12);
          cal.set(Calendar.MINUTE, 12);
          cal.set(Calendar.SECOND, 21);
          cal.set(Calendar.MILLISECOND, 0);
          cal.set(Calendar.ZONE_OFFSET, 0);
          getRequest.timestamp = cal.getTime();
          ByteArrayOutputStream bos=new ByteArrayOutputStream();
          getRequest.ber_encode(bos);
          byte[] bs=bos.toByteArray();
          for(int i=0; i<bs.length; i++) {
             System.out.printf("%02X ", bs[i] & 0xFF);
          }
       }
    
    }
  13. Compile the project if the Build automatically is turn off.
  14. Right click the file TestMyHttp.java and select Run as > Java Application:

    30 2D 80 01 FF 81 01 00 A2 04 80 02 04 C0 83 0E 77 77 77 2E 61 73 6E 6C 61 62 2E 6F 72 67 84 0F 32 30 31 32 31 32 32 31 31 32 31 32 32 31 5A

Here's the explanation of the encoded bits and bytes in BER:

0x30 -- [0011|0000], [UNIVERSAL, CONSTRUCTED, 16(SEQUENCE)] - GetRequest
0x2D -- [0010|1101], length 45

0x80 -- [1000|0000], [CONTEXT, PRIMITIVE, 0(BOOLEAN)] GetRequest.header_only
0x01 -- [0000|0001], length 1
0xFF -- [0000|1111], value TRUE

0x81 -- [1000|0001], [CONTEXT, PRIMITIVE, 1(BOOLEAN)] GetRequest.lock
0x01 -- [0000|0001], length 1
0x00 -- [0000|0000], value FALSE

0xA2 -- [1010|0010], [CONTEXT, CONSTRUCTED, 2(SET)] - GetRequest.accept_types
0x04 -- [0000|0100], length 4

0x80 -- [1000|0000], [CONTEXT, PRIMITIVE, 0(BIT STRING)] AcceptTypes.standards
0x02 -- [0000|0010], length 2
0x04 -- [0000|0100], 4 unused bits
0xC0 -- [1100|0000], {html, plaint_text}

0x83 -- [1000|0011], [CONTEXT, PRIMITIVE, 3(VisibleString)] GetRequest.url
0x0E -- [0000|1100], length 14
0x77 0x77 0x77 0x2E 0x61 0x73 0x6E 0x6C 0x61 0x62 0x2E 0x6F 0x72 0x67 -- www.asnlab.org

0x84 -- [1000|0011], [CONTEXT, PRIMITIVE, 4(GeneralizedTime)] GetRequest.timestamp
0x0F -- [0000|1100], length 15
0x32 0x30 0x31 0x32 0x31 0x32 0x32 0x31 0x31 0x32 0x31 0x32 0x32 0x31 0x5A -- 20121221121221Z

More Information

For more information regarding ASN.1 Runtime Library, please refer to the ASN.1 Java Runtime Library User Guide.