ballerina/mime package
Package Overview
This package provides functions to transmit and receive messages that have multiple parts, such as an attachment. The communication of such messages follow the MIME (Multipurpose Internet Mail Extensions) specification as specified in the RFC 2045 standard.
MIME Specific terms
The following terms are MIME specific and are extracted from the MIME specification.
Entity
This refers to the header fields and the content of a message, or a part of the body in a multipart entity.
Body Part
This refers to an entity that is inside a multipart entity.
Body
This is the body of an entity, which can be a body of a message or the body of a multipart entity.
Header Fields
Content-Type, Content-Transfer-Encoding, Content-ID, Content-Description, and Content-Disposition are some MIME header fields. These headers exist along with the other headers in the Entity
.
Content-Type: image/jpeg
Content-Disposition: attachment; filename=genome.jpeg;
Content-Description: a complete map of the human genome
Modify and retrieve the data in an Entity
The package provides functions to set and get an entity body from different kinds of message types. For example, XML, text, JSON, blob, and body parts. Headers can be modified through functions such as addHeader()
, setHeader()
, `removeHeader(), etc.
Samples
Handle multipart request
The sample service given below handles a multipart request. It gets the message from each part of the body, converts the messages to a string
, and sends a response.
import ballerina/http;
import ballerina/io;
import ballerina/mime;
endpoint http:Listener mockEP {
port:9090
};
@http:ServiceConfig {basePath:"/test"}
service<http:Service> test bind mockEP {
@http:ResourceConfig {
methods:["POST"],
path:"/multipleparts"
}
// The resource that handles multipart requests.
multipartResource(endpoint client, http:Request request) {
http:Response response = new;
// Get the body parts from the request.
match request.getBodyParts() {
// If there is an error while getting the body parts, set the response code as 500 and set the error message as the response message.
mime:EntityError err => {
response.statusCode = 500;
response.setStringPayload(err.message);
}
// If the body parts were returned, iterate through each body part and handle the content.
mime:Entity[] bodyParts => {
string content = "";
int i = 0;
while (i < lengthof bodyParts) {
mime:Entity part = bodyParts[i];
content = content + " -- " + handleContent(part);
i = i + 1;
}
response.setStringPayload(content);
}
}
_ = client -> respond(response);
}
}
// The function that handles the content based on the body part type.
function handleContent(mime:Entity bodyPart) returns (string) {
// Getting the base type of the specific body part.
string baseType = bodyPart.contentType.getBaseType();
// If the base type is ‘application/xml’ or ‘text/xml’, get the XML content from body part.
if (mime:APPLICATION_XML == baseType || mime:TEXT_XML == baseType) {
var payload = bodyPart.getXml();
match payload {
mime:EntityError err => return "Error in getting xml payload";
xml xmlContent => return xmlContent.getTextValue();
}
} else if (mime:APPLICATION_JSON == baseType) {
// If the base type is ‘application/json’, get the JSON content from body part.
var payload = bodyPart.getJson();
match payload {
mime:EntityError err => return "Error in getting json payload";
json jsonContent => {
return jsonContent.toString();
}
}
}
return "";
}
The sample request that is sent to the above service and the response that is printed on the console are shown below.
curl -v -F "request={\"param1\": \"value1\"};type=application/json" -F "language=ballerina;type=text/plain" -F "upload=@/home/megala/encode.txt;type=application/octet-stream" http://localhost:9090/test/multipleparts -H "Expect:"
* Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9090 (#0)
> POST /test/multipleparts HTTP/1.1
> Host: localhost:9090
> User-Agent: curl/7.47.0
> Accept: */*
> Content-Length: 521
> Content-Type: multipart/form-data; boundary=------------------------bf3f6dafe84260f2
>
< HTTP/1.1 200 OK
< content-type: text/plain
< content-length: 77
< server: ballerina/0.970.0-beta1-SNAPSHOT
< date: Wed, 18 Apr 2018 22:20:48 +0530
<
-- {"param1":"value1"} -- ballerina -- VGhpcyBpcyBhIGJhbGxlcmluYSBzYW1wbGU=
Create a multipart response
The sample given below creates a multipart response. It includes ‘application/json’ and ‘text/xml’ type content.
// Create a new body part.
mime:Entity bodyPart1 = new;
// Set the content type as ‘application/json’.
bodyPart1.contentType = mime:getMediaType(mime:APPLICATION_JSON);
// Finally, set the JSON content.
bodyPart1.setJson({"bodyPart":"jsonPart"});
// Create body part using an XML file.
mime:Entity bodyPart2 = new;
mime:MediaType textXml = mime:getMediaType(mime:TEXT_XML);
bodyPart2.contentType = textXml;
file:Path fileHandler = new("ballerina/mime/file.xml");
bodyPart2.setFileAsEntityBody(fileHandler);
//Create an array to hold all the body parts.
mime:Entity[] bodyParts = [bodyPart1, bodyPart2];
// Set the body parts to the outbound response.
http:Response outResponse = new;
// Set the content type as ‘multipart/mixed’ and set the body parts.
outResponse.setBodyParts(bodyParts, mime:MULTIPART_MIXED);
Objects Summary
Object | Description | ||
---|---|---|---|
ContentDisposition | Represent values in Content-Disposition header. |
||
Entity | Represent the headers and body of a message. This can be used to represent both the entity of a top level message and an entity(body part) inside of a multipart entity. |
||
MediaType | Describes the nature of the data in the body of a MIME entity. |
Functions Summary
Return Type | Function and Description | ||
---|---|---|---|
blob | error | base64DecodeBlob(blob valueToBeDecoded) Decode a given blob with Base64 encoding scheme. |
||
ioByteChannel | error | base64DecodeByteChannel(ByteChannel valueToBeDecoded) Decode a given ByteChannel with Base64 encoding scheme. |
||
string | error | base64DecodeString(string valueToBeDecoded) Decode a given string with Base64 encoding scheme. |
||
blob | error | base64EncodeBlob(blob valueToBeEncoded) Encode a given blob with Base64 encoding scheme. |
||
ioByteChannel | error | base64EncodeByteChannel(ByteChannel valueToBeEncoded) Encode a given ByteChannel with Base64 encoding scheme. |
||
string | error | base64EncodeString(string valueToBeEncoded) Encode a given string with Base64 encoding scheme. |
||
ContentDisposition | getContentDispositionObject(string contentDisposition) Given the Content-Disposition as a string, get the ContentDisposition object with it. |
||
MediaType | error | getMediaType(string contentType) Given the Content-Type in string, get the MediaType object populated with it. |
Global Variables
Name | Data Type | Description | |
---|---|---|---|
APPLICATION_FORM_URLENCODED | string | Represent 'application/x-www-form-urlencoded' media type. |
|
APPLICATION_JSON | string | Represent 'application/json' media type. |
|
APPLICATION_OCTET_STREAM | string | Represent 'application/octet-stream' media type. |
|
APPLICATION_PDF | string | Represent 'application/pdf' media type. |
|
APPLICATION_SVG_XML | string | Represent 'application/svg+xml' media type. |
|
APPLICATION_XHTML_XML | string | Represent 'application/xhtml+xml' media type. |
|
APPLICATION_XML | string | Represent 'application/xml' media type. |
|
BOUNDARY | string | Key name for 'boundary' parameter in MediaType. This is needed for composite type media types. |
|
CHARSET | string | Key name for 'charset' parameter in MediaType. Indicate the character set of the body text. |
|
CONTENT_DISPOSITION | string | Represent 'content-disposition' header name. |
|
CONTENT_ID | string | Represent 'content-id' header name. |
|
CONTENT_LENGTH | string | Represent 'content-length' header name. |
|
CONTENT_TYPE | string | Represent 'content-type' header name. |
|
DEFAULT_CHARSET | string | Default charset to be used with MIME encoding and decoding. |
|
IMAGE_GIF | string | Represent 'image/gif' media type. |
|
IMAGE_JPEG | string | Represent 'image/jpeg' media type. |
|
IMAGE_PNG | string | Represent 'image/png' media type. |
|
MULTIPART_ALTERNATIVE | string | Represent 'multipart/alternative' media type. |
|
MULTIPART_FORM_DATA | string | Represent 'multipart/form-data' media type. |
|
MULTIPART_MIXED | string | Represent 'multipart/mixed' media type. |
|
MULTIPART_PARALLEL | string | Represent 'multipart/parallel' media type. |
|
MULTIPART_RELATED | string | Represent 'multipart/related' media type. |
|
START | string | Key name for 'start' parameter in MediaType. This determines which part in the multipart message contains the payload. |
|
TEXT_HTML | string | Represent 'text/html' media type. |
|
TEXT_PLAIN | string | Represent 'text/plain' media type. |
|
TEXT_XML | string | Represent 'text/xml' media type. |
|
TYPE | string | Key name for 'type' parameter in MediaType. This indicates the MIME media type of the 'root' body part. |
public function base64DecodeBlob(blob valueToBeDecoded) returns (blob | error)
Decode a given blob with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeDecoded | blob | Content that needs to be decoded |
Return Type | Description | ||
---|---|---|---|
blob | error | Return a decoded |
public function base64DecodeByteChannel(ByteChannel valueToBeDecoded) returns (ioByteChannel | error)
Decode a given ByteChannel with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeDecoded | ByteChannel | Content that needs to be decoded |
Return Type | Description | ||
---|---|---|---|
ioByteChannel | error | Return a decoded |
public function base64DecodeString(string valueToBeDecoded) returns (string | error)
Decode a given string with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeDecoded | string | Content that needs to be decoded |
Return Type | Description | ||
---|---|---|---|
string | error | Return a decoded |
public function base64EncodeBlob(blob valueToBeEncoded) returns (blob | error)
Encode a given blob with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeEncoded | blob | Content that needs to be encoded |
Return Type | Description | ||
---|---|---|---|
blob | error | Return an encoded blob. An |
public function base64EncodeByteChannel(ByteChannel valueToBeEncoded) returns (ioByteChannel | error)
Encode a given ByteChannel with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeEncoded | ByteChannel | Content that needs to be encoded
Return an encoded |
Return Type | Description | ||
---|---|---|---|
ioByteChannel | error |
public function base64EncodeString(string valueToBeEncoded) returns (string | error)
Encode a given string with Base64 encoding scheme.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
valueToBeEncoded | string | Content that needs to be encoded |
Return Type | Description | ||
---|---|---|---|
string | error | Return an encoded |
public function getContentDispositionObject(string contentDisposition) returns (ContentDisposition)
Given the Content-Disposition as a string, get the ContentDisposition object with it.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
contentDisposition | string | content disposition string |
Return Type | Description | ||
---|---|---|---|
ContentDisposition | Return a |
public function getMediaType(string contentType) returns (MediaType | error)
Given the Content-Type in string, get the MediaType object populated with it.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
contentType | string | Content-Type in string |
Return Type | Description | ||
---|---|---|---|
MediaType | error | Return |
public type ContentDisposition object
Represent values in Content-Disposition header.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
fileName | string | Default filename for storing the bodypart, if the receiving agent wishes to store it in an external file |
|
disposition | string | Indicates how the body part should be presented (inline, attachment or as form-data) |
|
name | string | Represent the field name in case of 'multipart/form-data' |
|
parameters | map<string> | A set of parameters, specified in attribute=value notation |
-
<ContentDisposition> toString() returns (string)
Convert the ContentDisposition type to a string suitable for use as the value of a corresponding MIME header.
Return Type Description string Return a
string
represnetation ofContentDisposition
object
public type Entity object
Represent the headers and body of a message. This can be used to represent both the entity of a top level message and an entity(body part) inside of a multipart entity.
-
<Entity> setContentType(string mediaType)
Set the content-type to entity.
Parameter Name Data Type Default Value Description mediaType string content-type that needs to be set to entity
-
<Entity> getContentType() returns (string)
Get the content-type of entity.
Return Type Description string Return content-type as a
string
-
<Entity> setContentId(string contentId)
Set the content-id of the entity.
Parameter Name Data Type Default Value Description contentId string content-id that needs to be set to entity
-
<Entity> getContentId() returns (string)
Get the content-id of entity.
Return Type Description string Return content-id as a
string
-
<Entity> setContentLength(int contentLength)
Set the content-length of the entity.
Parameter Name Data Type Default Value Description contentLength int content-length that needs to be set to entity
-
<Entity> getContentLength() returns (int | error)
Get the content-length of entity.
Return Type Description int | error Return content-length as an
int
-
<Entity> setContentDisposition(ContentDisposition contentDisposition)
Set the content-disposition of the entity.
Parameter Name Data Type Default Value Description contentDisposition ContentDisposition content-disposition that needs to be set to entity
-
<Entity> getContentDisposition() returns (ContentDisposition)
Get the content-disposition of entity.
Return Type Description ContentDisposition Return a
ContentDisposition
object -
<Entity> setBody(string | xml | json | blob | ioByteChannel | Entity[] entityBody)
Set the entity body with a given content.
Parameter Name Data Type Default Value Description entityBody string | xml | json | blob | ioByteChannel | Entity[] Entity body can be of type
string
,xml
,json
,blob
,io:ByteChannel
orEntity[]
-
<Entity> setFileAsEntityBody(string filePath)
Set the entity body with a given file. This method will override any existing content-type headers with the default content-type 'application/octec-stream'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description filePath string Represent the path to the file
-
<Entity> setJson(json jsonContent)
Set the entity body with the given json content. This method will override any existing content-type headers with the default content-type 'application/json'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description jsonContent json Json content that needs to be set to entity
-
<Entity> getJson() returns (json | error)
Extract json body from the entity. If the entity body is not json compatible an error will be returned.
Return Type Description json | error Return
json
data extracted from the the entity body. Anerror
record will be returned in case of errors. -
<Entity> setXml(xml xmlContent)
Set the entity body with the given xml content. This method will override any existing content-type headers with the default content-type 'application/xml'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description xmlContent xml Xml content that needs to be set to entity
-
<Entity> getXml() returns (xml | error)
Extract xml body from the entity. If the entity body is not xml compatible an error will be returned.
Return Type Description xml | error Return
xml
data extracted from the the entity body. Anerror
record will be returned in case of errors. -
<Entity> setText(string textContent)
Set the entity body with the given text content. This method will override any existing content-type headers with the default content-type 'text/plain'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description textContent string Text content that needs to be set to entity
-
<Entity> getText() returns (string | error)
Extract text body from the entity. If the entity body is not text compatible an error will be returned.
Return Type Description string | error Return
string
data extracted from the the entity body. Anerror
record will be returned in case of errors. -
<Entity> getBodyAsString() returns (string | error)
Given an entity, get the entity body as a string. Content-type will not be checked during entity body construction which makes this different from getText() method.
Return Type Description string | error Return entity body as a
string
. Anerror
record will be returned in case of errors occurred during construction of the string body. -
<Entity> setBlob(blob blobContent)
Set the entity body with the given blob content. This method will override any existing content-type headers with the default content-type 'application/octec-stream'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description blobContent blob Blob content that needs to be set to entity
-
<Entity> getBlob() returns (blob | error)
Given an entity, get the entity body as a blob. If the entity size is considerably large consider using getByteChannel() method instead.
Return Type Description blob | error Return
blob
data extracted from the the entity body. Anerror
record will be returned in case of errors. -
<Entity> setByteChannel(ByteChannel byteChannel)
Set the entity body with the given byte channel content. This method will override any existing content-type headers with the default content-type 'application/octec-stream'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description byteChannel ByteChannel Byte channel that needs to be set to entity
-
<Entity> getByteChannel() returns (ioByteChannel | error)
Given an entity, get the entity body as a byte channel.
Return Type Description ioByteChannel | error Return an
io:ByteChannel
. Anerror
record will be returned in case of errors -
<Entity> getBodyParts() returns (Entity[] | error)
Given an entity, get its body parts. If the entity body is not a set of body parts an error will be returned.
Return Type Description Entity[] | error Return an array of body parts(
Entity[]
) extracted from the entity body. Anerror
record will be returned in case of errors -
<Entity> getBodyPartsAsChannel() returns (ByteChannel)
Given an entity, get the body parts as a byte channel.
Return Type Description ByteChannel Return body parts as a byte channel
-
<Entity> setBodyParts(Entity[] bodyParts)
Set body parts to entity. This method will override any existing content-type headers with the default content-type 'multipart/form-data'. You can override the default value by passing the content-type as an optional parameter.
Parameter Name Data Type Default Value Description bodyParts Entity[] Represent the body parts that needs to be set to the entity
-
<Entity> getHeader(string headerName) returns (string)
Get the header value associated with the given header name.
Parameter Name Data Type Default Value Description headerName string Represent header name
Return Type Description string Return header value associated with the given header name as a
string
. If multiple header values are present, then the first value will be returned -
<Entity> getHeaders(string headerName) returns (string[])
Get all the header values associated with the given header name.
Parameter Name Data Type Default Value Description headerName string Represent the header name
Return Type Description string[] Return all the header values associated with the given header name as a
string[]
-
<Entity> getHeaderNames() returns (string[])
Get all header names.
Return Type Description string[] Return all header names as a
string[]
-
<Entity> addHeader(string headerName, string headerValue)
Add the given header value against the given header.
Parameter Name Data Type Default Value Description headerName string Represent the header name
headerValue string Represent the header value to be added
-
<Entity> setHeader(string headerName, string headerValue)
Set the given header value against the given header. If a header already exist, its value will be replaced with the given header value.
Parameter Name Data Type Default Value Description headerName string Represent the header name
headerValue string Represent the header value
-
<Entity> removeHeader(string headerName)
Remove the given header from the entity.
Parameter Name Data Type Default Value Description headerName string Represent the header name
-
<Entity> removeAllHeaders()
Remove all headers associated with the entity.
-
<Entity> hasHeader(string headerName) returns (boolean)
Check the header existence.
Parameter Name Data Type Default Value Description headerName string Return Type Description boolean
public type MediaType object
Describes the nature of the data in the body of a MIME entity.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
primaryType | string | Declares the general type of data |
|
subType | string | A specific format of the primary type data |
|
suffix | string | Identify the semantics of a specific media type |
|
parameters | map<string> | A set of parameters, specified in an attribute=value notation |
-
<MediaType> getBaseType() returns (string)
Get ���primaryType/subtype+suffix��� combination in string format.
Return Type Description string Return base type as a
string
from MediaType struct -
<MediaType> toString() returns (string)
Convert the media type to a string, suitable to be used as the value of a corresponding HTTP header.
Return Type Description string Return the content-type with parameters as a
string