Paho MQTT 5
Since Camel 3.8
Both producer and consumer are supported
Paho MQTT5 component provides connector for the MQTT messaging protocol using the Eclipse Paho library with MQTT v5. Paho is one of the most popular MQTT libraries, so if you would like to integrate it with your Java project - Camel Paho connector is a way to go.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-paho-mqtt5</artifactId>
<version>x.y.z</version>
<!-- use the same version as your Camel core version -->
</dependency>Configuring Options
Camel components are configured on two separate levels:
-
component level
-
endpoint level
Configuring Component Options
The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.
Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.
Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.
Configuring Endpoint Options
Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.
Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.
A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.
The following two sections lists all the options, firstly for the component followed by the endpoint.
Component Options
The Paho MQTT 5 component supports 32 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
Sets whether the client will automatically attempt to reconnect to the server if the connection is lost. <ul> <li>If set to false, the client will not attempt to automatically reconnect to the server in the event that the connection is lost. <li>If set to true, in the event that the connection is lost, the client will attempt to reconnect to the server. It will initially wait 1 second before it attempts to reconnect, for every failed reconnect attempt, the delay will double until it is at 2 minutes at which point the delay will stay at 2 minutes. |
true |
boolean |
|
The URL of the MQTT broker. |
tcp://localhost:1883 |
String |
|
Sets whether the client and server should remember state across restarts and reconnects. <ul> <li>If set to false both the client and server will maintain state across restarts of the client, the server and the connection. As state is maintained: <ul> <li>Message delivery will be reliable meeting the specified QOS even if the client, server or connection are restarted. <li>The server will treat a subscription as durable. <li>If set to true the client and server will not maintain state across restarts of the client, the server or the connection. This means <ul> <li>Message delivery to the specified QOS cannot be maintained if the client, server or connection are restarted <li>The server will treat a subscription as non-durable. |
true |
boolean |
|
MQTT client identifier. The identifier must be unique. |
String |
||
To use the shared Paho configuration. |
PahoMqtt5Configuration |
||
Sets the connection timeout value. This value, measured in seconds, defines the maximum time interval the client will wait for the network connection to the MQTT server to be established. The default timeout is 30 seconds. A value of 0 disables timeout processing meaning the client will wait until the network connection is made successfully or fails. |
30 |
int |
|
Base directory used by file persistence. Will by default use user directory. |
String |
||
Sets the keep alive interval. This value, measured in seconds, defines the maximum time interval between messages sent or received. It enables the client to detect if the server is no longer available, without having to wait for the TCP/IP timeout. The client will ensure that at least one message travels across the network within each keep alive period. In the absence of a data-related message during the time period, the client sends a very small ping message, which the server will acknowledge. A value of 0 disables keepalive processing in the client. <p> The default value is 60 seconds. |
60 |
int |
|
Get the maximum time (in millis) to wait between reconnects. |
128000 |
int |
|
Client persistence to be used - memory or file. Enum values:
|
MEMORY |
PahoMqtt5Persistence |
|
Client quality of service level (0-2). |
2 |
int |
|
Sets the Receive Maximum. This value represents the limit of QoS 1 and QoS 2 publications that the client is willing to process concurrently. There is no mechanism to limit the number of QoS 0 publications that the Server might try to send. <p> The default value is 65535. |
65535 |
int |
|
Retain option. |
false |
boolean |
|
Set a list of one or more serverURIs the client may connect to. Multiple servers can be separated by comma. <p> Each <code>serverURI specifies the address of a server that the client may connect to. Two types of connection are supported <code>tcp:// for a TCP connection and <code>ssl:// for a TCP connection secured by SSL/TLS. For example: <ul> <li><code>tcp://localhost:1883 <li><code>ssl://localhost:8883 If the port is not specified, it will default to 1883 for <code>tcp:// URIs, and 8883 for <code>ssl:// URIs. <p> If serverURIs is set then it overrides the serverURI parameter passed in on the constructor of the MQTT client. <p> When an attempt to connect is initiated the client will start with the first serverURI in the list and work through the list until a connection is established with a server. If a connection cannot be made to any of the servers then the connect attempt fails. <p> Specifying a list of servers that a client may connect to has several uses: <ol> <li>High Availability and reliable message delivery <p> Some MQTT servers support a high availability feature where two or more equal MQTT servers share state. An MQTT client can connect to any of the equal servers and be assured that messages are reliably delivered and durable subscriptions are maintained no matter which server the client connects to. <p> The cleansession flag must be set to false if durable subscriptions and/or reliable message delivery is required. <li>Hunt List <p> A set of servers may be specified that are not equal (as in the high availability option). As no state is shared across the servers reliable message delivery and durable subscriptions are not valid. The cleansession flag must be set to true if the hunt list mode is used. |
String |
||
Sets the Session Expiry Interval. This value, measured in seconds, defines the maximum time that the broker will maintain the session for once the client disconnects. Clients should only connect with a long Session Expiry interval if they intend to connect to the server at some later point in time. By default this value is -1 and so will not be sent, in this case, the session will not expire. If a 0 is sent, the session will end immediately once the Network Connection is closed. When the client has determined that it has no longer any use for the session, it should disconnect with a Session Expiry Interval set to 0. |
-1 |
long |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The MQTT properties set for the message. |
MqttProperties |
||
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The byte payload for the message. |
String |
||
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The quality of service to publish the message at (0, 1 or 2). |
1 |
int |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. Whether or not the message should be retained. |
false |
boolean |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The topic to publish to. |
String |
||
Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. |
false |
boolean |
|
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
boolean |
|
Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. |
true |
boolean |
|
To use a shared Paho client. |
MqttClient |
||
Sets the Custom WebSocket Headers for the WebSocket Connection. |
Map |
||
Set the time in seconds that the executor service should wait when terminating before forcefully terminating. It is not recommended to change this value unless you are absolutely sure that you need to. |
1 |
int |
|
Whether SSL HostnameVerifier is enabled or not. The default value is true. |
true |
boolean |
|
Password to be used for authentication against the MQTT broker. |
String |
||
Sets the SocketFactory to use. This allows an application to apply its own policies around the creation of network sockets. If using an SSL connection, an SSLSocketFactory can be used to supply application-specific security settings. |
SocketFactory |
||
Sets the SSL properties for the connection. <p> Note that these properties are only valid if an implementation of the Java Secure Socket Extensions (JSSE) is available. These properties are <em>not used if a custom SocketFactory has been set. The following properties can be used: <dl> <dt>com.ibm.ssl.protocol <dd>One of: SSL, SSLv3, TLS, TLSv1, SSL_TLS. <dt>com.ibm.ssl.contextProvider <dd>Underlying JSSE provider. For example IBMJSSE2 or SunJSSE <dt>com.ibm.ssl.keyStore <dd>The name of the file that contains the KeyStore object that you want the KeyManager to use. For example /mydir/etc/key.p12 <dt>com.ibm.ssl.keyStorePassword <dd>The password for the KeyStore object that you want the KeyManager to use. The password can either be in plain-text, or may be obfuscated using the static method: <code>com.ibm.micro.security.Password.obfuscate(char password). This obfuscates the password using a simple and insecure XOR and Base64 encoding mechanism. Note that this is only a simple scrambler to obfuscate clear-text passwords. <dt>com.ibm.ssl.keyStoreType <dd>Type of key store, for example PKCS12, JKS, or JCEKS. <dt>com.ibm.ssl.keyStoreProvider <dd>Key store provider, for example IBMJCE or IBMJCEFIPS. <dt>com.ibm.ssl.trustStore <dd>The name of the file that contains the KeyStore object that you want the TrustManager to use. <dt>com.ibm.ssl.trustStorePassword <dd>The password for the TrustStore object that you want the TrustManager to use. The password can either be in plain-text, or may be obfuscated using the static method: <code>com.ibm.micro.security.Password.obfuscate(char password). This obfuscates the password using a simple and insecure XOR and Base64 encoding mechanism. Note that this is only a simple scrambler to obfuscate clear-text passwords. <dt>com.ibm.ssl.trustStoreType <dd>The type of KeyStore object that you want the default TrustManager to use. Same possible values as keyStoreType. <dt>com.ibm.ssl.trustStoreProvider <dd>Trust store provider, for example IBMJCE or IBMJCEFIPS. <dt>com.ibm.ssl.enabledCipherSuites <dd>A list of which ciphers are enabled. Values are dependent on the provider, for example: SSL_RSA_WITH_AES_128_CBC_SHA;SSL_RSA_WITH_3DES_EDE_CBC_SHA. <dt>com.ibm.ssl.keyManager <dd>Sets the algorithm that will be used to instantiate a KeyManagerFactory object instead of using the default algorithm available in the platform. Example values: IbmX509 or IBMJ9X509. <dt>com.ibm.ssl.trustManager <dd>Sets the algorithm that will be used to instantiate a TrustManagerFactory object instead of using the default algorithm available in the platform. Example values: PKIX or IBMJ9X509. |
Properties |
||
Sets the HostnameVerifier for the SSL connection. Note that it will be used after handshake on a connection and you should do actions by yourself when hostname is verified error. <p> There is no default HostnameVerifier. |
HostnameVerifier |
||
Username to be used for authentication against the MQTT broker. |
String |
Endpoint Options
The Paho MQTT 5 endpoint is configured using URI syntax:
paho-mqtt5:topic
with the following path and query parameters:
Query Parameters (32 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
Sets whether the client will automatically attempt to reconnect to the server if the connection is lost. <ul> <li>If set to false, the client will not attempt to automatically reconnect to the server in the event that the connection is lost. <li>If set to true, in the event that the connection is lost, the client will attempt to reconnect to the server. It will initially wait 1 second before it attempts to reconnect, for every failed reconnect attempt, the delay will double until it is at 2 minutes at which point the delay will stay at 2 minutes. |
true |
boolean |
|
The URL of the MQTT broker. |
tcp://localhost:1883 |
String |
|
Sets whether the client and server should remember state across restarts and reconnects. <ul> <li>If set to false both the client and server will maintain state across restarts of the client, the server and the connection. As state is maintained: <ul> <li>Message delivery will be reliable meeting the specified QOS even if the client, server or connection are restarted. <li>The server will treat a subscription as durable. <li>If set to true the client and server will not maintain state across restarts of the client, the server or the connection. This means <ul> <li>Message delivery to the specified QOS cannot be maintained if the client, server or connection are restarted <li>The server will treat a subscription as non-durable. |
true |
boolean |
|
MQTT client identifier. The identifier must be unique. |
String |
||
Sets the connection timeout value. This value, measured in seconds, defines the maximum time interval the client will wait for the network connection to the MQTT server to be established. The default timeout is 30 seconds. A value of 0 disables timeout processing meaning the client will wait until the network connection is made successfully or fails. |
30 |
int |
|
Base directory used by file persistence. Will by default use user directory. |
String |
||
Sets the keep alive interval. This value, measured in seconds, defines the maximum time interval between messages sent or received. It enables the client to detect if the server is no longer available, without having to wait for the TCP/IP timeout. The client will ensure that at least one message travels across the network within each keep alive period. In the absence of a data-related message during the time period, the client sends a very small ping message, which the server will acknowledge. A value of 0 disables keepalive processing in the client. <p> The default value is 60 seconds. |
60 |
int |
|
Get the maximum time (in millis) to wait between reconnects. |
128000 |
int |
|
Client persistence to be used - memory or file. Enum values:
|
MEMORY |
PahoMqtt5Persistence |
|
Client quality of service level (0-2). |
2 |
int |
|
Sets the Receive Maximum. This value represents the limit of QoS 1 and QoS 2 publications that the client is willing to process concurrently. There is no mechanism to limit the number of QoS 0 publications that the Server might try to send. <p> The default value is 65535. |
65535 |
int |
|
Retain option. |
false |
boolean |
|
Set a list of one or more serverURIs the client may connect to. Multiple servers can be separated by comma. <p> Each <code>serverURI specifies the address of a server that the client may connect to. Two types of connection are supported <code>tcp:// for a TCP connection and <code>ssl:// for a TCP connection secured by SSL/TLS. For example: <ul> <li><code>tcp://localhost:1883 <li><code>ssl://localhost:8883 If the port is not specified, it will default to 1883 for <code>tcp:// URIs, and 8883 for <code>ssl:// URIs. <p> If serverURIs is set then it overrides the serverURI parameter passed in on the constructor of the MQTT client. <p> When an attempt to connect is initiated the client will start with the first serverURI in the list and work through the list until a connection is established with a server. If a connection cannot be made to any of the servers then the connect attempt fails. <p> Specifying a list of servers that a client may connect to has several uses: <ol> <li>High Availability and reliable message delivery <p> Some MQTT servers support a high availability feature where two or more equal MQTT servers share state. An MQTT client can connect to any of the equal servers and be assured that messages are reliably delivered and durable subscriptions are maintained no matter which server the client connects to. <p> The cleansession flag must be set to false if durable subscriptions and/or reliable message delivery is required. <li>Hunt List <p> A set of servers may be specified that are not equal (as in the high availability option). As no state is shared across the servers reliable message delivery and durable subscriptions are not valid. The cleansession flag must be set to true if the hunt list mode is used. |
String |
||
Sets the Session Expiry Interval. This value, measured in seconds, defines the maximum time that the broker will maintain the session for once the client disconnects. Clients should only connect with a long Session Expiry interval if they intend to connect to the server at some later point in time. By default this value is -1 and so will not be sent, in this case, the session will not expire. If a 0 is sent, the session will end immediately once the Network Connection is closed. When the client has determined that it has no longer any use for the session, it should disconnect with a Session Expiry Interval set to 0. |
-1 |
long |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The MQTT properties set for the message. |
MqttProperties |
||
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The byte payload for the message. |
String |
||
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The quality of service to publish the message at (0, 1 or 2). |
1 |
int |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. Whether or not the message should be retained. |
false |
boolean |
|
Sets the Last Will and Testament (LWT) for the connection. In the event that this client unexpectedly loses its connection to the server, the server will publish a message to itself using the supplied details. The topic to publish to. |
String |
||
Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. |
false |
boolean |
|
To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored. |
ExceptionHandler |
||
Sets the exchange pattern when the consumer creates an exchange. Enum values:
|
ExchangePattern |
||
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
boolean |
|
To use an existing mqtt client. |
MqttClient |
||
Sets the Custom WebSocket Headers for the WebSocket Connection. |
Map |
||
Set the time in seconds that the executor service should wait when terminating before forcefully terminating. It is not recommended to change this value unless you are absolutely sure that you need to. |
1 |
int |
|
Whether SSL HostnameVerifier is enabled or not. The default value is true. |
true |
boolean |
|
Password to be used for authentication against the MQTT broker. |
String |
||
Sets the SocketFactory to use. This allows an application to apply its own policies around the creation of network sockets. If using an SSL connection, an SSLSocketFactory can be used to supply application-specific security settings. |
SocketFactory |
||
Sets the SSL properties for the connection. <p> Note that these properties are only valid if an implementation of the Java Secure Socket Extensions (JSSE) is available. These properties are <em>not used if a custom SocketFactory has been set. The following properties can be used: <dl> <dt>com.ibm.ssl.protocol <dd>One of: SSL, SSLv3, TLS, TLSv1, SSL_TLS. <dt>com.ibm.ssl.contextProvider <dd>Underlying JSSE provider. For example IBMJSSE2 or SunJSSE <dt>com.ibm.ssl.keyStore <dd>The name of the file that contains the KeyStore object that you want the KeyManager to use. For example /mydir/etc/key.p12 <dt>com.ibm.ssl.keyStorePassword <dd>The password for the KeyStore object that you want the KeyManager to use. The password can either be in plain-text, or may be obfuscated using the static method: <code>com.ibm.micro.security.Password.obfuscate(char password). This obfuscates the password using a simple and insecure XOR and Base64 encoding mechanism. Note that this is only a simple scrambler to obfuscate clear-text passwords. <dt>com.ibm.ssl.keyStoreType <dd>Type of key store, for example PKCS12, JKS, or JCEKS. <dt>com.ibm.ssl.keyStoreProvider <dd>Key store provider, for example IBMJCE or IBMJCEFIPS. <dt>com.ibm.ssl.trustStore <dd>The name of the file that contains the KeyStore object that you want the TrustManager to use. <dt>com.ibm.ssl.trustStorePassword <dd>The password for the TrustStore object that you want the TrustManager to use. The password can either be in plain-text, or may be obfuscated using the static method: <code>com.ibm.micro.security.Password.obfuscate(char password). This obfuscates the password using a simple and insecure XOR and Base64 encoding mechanism. Note that this is only a simple scrambler to obfuscate clear-text passwords. <dt>com.ibm.ssl.trustStoreType <dd>The type of KeyStore object that you want the default TrustManager to use. Same possible values as keyStoreType. <dt>com.ibm.ssl.trustStoreProvider <dd>Trust store provider, for example IBMJCE or IBMJCEFIPS. <dt>com.ibm.ssl.enabledCipherSuites <dd>A list of which ciphers are enabled. Values are dependent on the provider, for example: SSL_RSA_WITH_AES_128_CBC_SHA;SSL_RSA_WITH_3DES_EDE_CBC_SHA. <dt>com.ibm.ssl.keyManager <dd>Sets the algorithm that will be used to instantiate a KeyManagerFactory object instead of using the default algorithm available in the platform. Example values: IbmX509 or IBMJ9X509. <dt>com.ibm.ssl.trustManager <dd>Sets the algorithm that will be used to instantiate a TrustManagerFactory object instead of using the default algorithm available in the platform. Example values: PKIX or IBMJ9X509. |
Properties |
||
Sets the HostnameVerifier for the SSL connection. Note that it will be used after handshake on a connection and you should do actions by yourself when hostname is verified error. <p> There is no default HostnameVerifier. |
HostnameVerifier |
||
Username to be used for authentication against the MQTT broker. |
String |
Headers
The following headers are recognized by the Paho component:
| Header | Java constant | Endpoint type | Value type | Description |
|---|---|---|---|---|
CamelMqttTopic |
PahoConstants.MQTT_TOPIC |
Consumer |
String |
The name of the topic |
CamelMqttQoS |
PahoConstants.MQTT_QOS |
Consumer |
Integer |
QualityOfService of the incoming message |
CamelPahoOverrideTopic |
PahoConstants.CAMEL_PAHO_OVERRIDE_TOPIC |
Producer |
String |
Name of topic to override and send to instead of topic specified on endpoint |
Default payload type
By default Camel Paho component operates on the binary payloads extracted out of (or put into) the MQTT message:
// Receive payload
byte[] payload = (byte[]) consumerTemplate.receiveBody("paho:topic");
// Send payload
byte[] payload = "message".getBytes();
producerTemplate.sendBody("paho:topic", payload);But of course Camel build-in type conversion
API can perform the automatic data type transformations for you. In the
example below Camel automatically converts binary payload into String
(and conversely):
// Receive payload
String payload = consumerTemplate.receiveBody("paho:topic", String.class);
// Send payload
String payload = "message";
producerTemplate.sendBody("paho:topic", payload);Samples
For example the following snippet reads messages from the MQTT broker installed on the same host as the Camel router:
from("paho:some/queue")
.to("mock:test");While the snippet below sends message to the MQTT broker:
from("direct:test")
.to("paho:some/target/queue");For example this is how to read messages from the remote MQTT broker:
from("paho:some/queue?brokerUrl=tcp://iot.eclipse.org:1883")
.to("mock:test");And here we override the default topic and set to a dynamic topic
from("direct:test")
.setHeader(PahoConstants.CAMEL_PAHO_OVERRIDE_TOPIC, simple("${header.customerId}"))
.to("paho:some/target/queue");Spring Boot Auto-Configuration
When using paho-mqtt5 with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:
<dependency>
<groupId>org.apache.camel.springboot</groupId>
<artifactId>camel-paho-mqtt5-starter</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>The component supports 33 options, which are listed below.