Chapter 189. JsonPath Language
Chapter 189. JsonPath Language Available as of Camel version 2.13 Camel supports JSonPath to allow using Expression or Predicate on json messages. from("queue:books.new") .choice() .when().jsonpath("USD.store.book[?(@.price < 10)]") .to("jms:queue:book.cheap") .when().jsonpath("USD.store.book[?(@.price < 30)]") .to("jms:queue:book.average") .otherwise() .to("jms:queue:book.expensive") 189.1. JSonPath Options The JsonPath language supports 7 options, which are listed below. Name Default Java Type Description resultType String Sets the class name of the result type (type from output) suppressExceptions false Boolean Whether to suppress exceptions such as PathNotFoundException. allowSimple true Boolean Whether to allow in inlined simple exceptions in the JsonPath expression allowEasyPredicate true Boolean Whether to allow using the easy predicate parser to pre-parse predicates. writeAsString false Boolean Whether to write the output of each row/element as a JSON String value instead of a Map/POJO value. headerName String Name of header to use as input, instead of the message body trim true Boolean Whether to trim the value to remove leading and trailing whitespaces and line breaks 189.2. Spring Boot Auto-Configuration The component supports 7 options, which are listed below. Name Description Default Type camel.language.jsonpath.allow-easy-predicate Whether to allow using the easy predicate parser to pre-parse predicates. true Boolean camel.language.jsonpath.allow-simple Whether to allow in inlined simple exceptions in the JsonPath expression true Boolean camel.language.jsonpath.enabled Enable jsonpath language true Boolean camel.language.jsonpath.header-name Name of header to use as input, instead of the message body String camel.language.jsonpath.suppress-exceptions Whether to suppress exceptions such as PathNotFoundException. false Boolean camel.language.jsonpath.trim Whether to trim the value to remove leading and trailing whitespaces and line breaks true Boolean camel.language.jsonpath.write-as-string Whether to write the output of each row/element as a JSON String value instead of a Map/POJO value. false Boolean 189.3. Using XML configuration If you prefer to configure your routes in your Spring XML file then you can use JSonPath expressions as follows <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring"> <route> <from uri="direct:start"/> <choice> <when> <jsonpath>USD.store.book[?(@.price &lt; 10)]</jsonpath> <to uri="mock:cheap"/> </when> <when> <jsonpath>USD.store.book[?(@.price &lt; 30)]</jsonpath> <to uri="mock:average"/> </when> <otherwise> <to uri="mock:expensive"/> </otherwise> </choice> </route> </camelContext> 189.4. Syntax See the JSonPath project page for further examples. 189.5. Easy Syntax Available as of Camel 2.19 When you just want to define a basic predicate using jsonpath syntax it can be a bit hard to remember the syntax. So for example to find out all the cheap books you have to do However what if you could just write it as And you can omit the path if you just want to look at nodes with a price key To support this there is a EasyPredicateParser which kicks-in if you have define the predicate using a basic style. That means the predicate must not start with the USD sign, and only include one operator. The easy syntax is: You can use Camel simple language in the right operator, eg 189.6. Supported message body types Camel JSonPath supports message body using the following types: Type Comment File Reading from files String Plain strings Map Message bodies as java.util.Map types List Message bodies as java.util.List types POJO Optional If Jackson is on the classpath, then camel-jsonpath is able to use Jackson to read the message body as POJO and convert to java.util.Map which is supported by JSonPath. For example you can add camel-jackson as dependency to include Jackson. InputStream If none of the above types matches, then Camel will attempt to read the message body as an java.io.InputStream . If a message body is of unsupported type then an exception is thrown by default, however you can configure JSonPath to suppress exceptions (see below) 189.7. Suppress exceptions Available as of Camel 2.16 By default jsonpath will throw an exception if the json payload does not have a valid path accordingly to the configured jsonpath expression. In some use-cases you may want to ignore this in case the json payload contains optional data. Therefore you can set the option suppressExceptions to true to ignore this as shown: from("direct:start") .choice() // use true to suppress exceptions .when().jsonpath("person.middlename", true) .to("mock:middle") .otherwise() .to("mock:other"); And in XML DSL: <route> <from uri="direct:start"/> <choice> <when> <jsonpath suppressExceptions="true">person.middlename</jsonpath> <to uri="mock:middle"/> </when> <otherwise> <to uri="mock:other"/> </otherwise> </choice> </route> This option is also available on the @JsonPath annotation. 189.8. Inline Simple exceptions Available as of Camel 2.18 Its now possible to inlined Simple language expressions in the JSonPath expression using the simple syntax USD{xxx}. An example is shown below: from("direct:start") .choice() .when().jsonpath("USD.store.book[?(@.price < USD{header.cheap})]") .to("mock:cheap") .when().jsonpath("USD.store.book[?(@.price < USD{header.average})]") .to("mock:average") .otherwise() .to("mock:expensive"); And in XML DSL: <route> <from uri="direct:start"/> <choice> <when> <jsonpath>USD.store.book[?(@.price < USD{header.cheap})]</jsonpath> <to uri="mock:cheap"/> </when> <when> <jsonpath>USD.store.book[?(@.price < USD{header.average})]</jsonpath> <to uri="mock:average"/> </when> <otherwise> <to uri="mock:expensive"/> </otherwise> </choice> </route> You can turn off support for inlined simple expression by setting the option allowSimple to false as shown: .when().jsonpath("USD.store.book[?(@.price < 10)]", false, false) And in XML DSL: <jsonpath allowSimple="false">USD.store.book[?(@.price < 10)]</jsonpath> 189.9. JSonPath injection You can use Bean Integration to invoke a method on a bean and use various languages such as JSonPath to extract a value from the message and bind it to a method parameter. For example public class Foo { @Consume(uri = "activemq:queue:books.new") public void doSomething(@JsonPath("USD.store.book[*].author") String author, @Body String json) { // process the inbound message here } } 189.10. Encoding Detection Since Camel version 2.16 , the encoding of the JSON document is detected automatically, if the document is encoded in unicode (UTF-8, UTF-16LE, UTF-16BE, UTF-32LE, UTF-32BE ) as specified in RFC-4627. If the encoding is a non-unicode encoding, you can either make sure that you enter the document in String format to the JSONPath component or you can specify the encoding in the header " CamelJsonPathJsonEncoding " (JsonpathConstants.HEADER_JSON_ENCODING). 189.11. Split JSon data into sub rows as JSon You can use jsonpath to split a JSon document, such as: from("direct:start") .split().jsonpath("USD.store.book[*]") .to("log:book"); Then each book is logged, however the message body is a Map instance. Sometimes you may want to output this as plain String JSon value instead, which can be done from Camel 2.20 onwards with the writeAsString option as shown: from("direct:start") .split().jsonpathWriteAsString("USD.store.book[*]") .to("log:book"); Then each book is logged as a String JSon value. For earlier versions of Camel you would need to use camel-jackson dataformat and marshal the message body to make it convert the message body from Map to a String type. 189.12. Using header as input Available as of Camel 2.20 By default jsonpath uses the message body as the input source. However you can also use a header as input by specifying the headerName option. For example to count the number of books from a json document that was stored in a header named books you can do: from("direct:start") .setHeader("numberOfBooks") .jsonpath("USD..store.book.length()", false, int.class, "books") .to("mock:result"); In the jsonpath expression above we specify the name of the header as books and we also told that we wanted the result to be converted as an integer by int.class . The same example in XML DSL would be: <route> <from uri="direct:start"/> <setHeader headerName="numberOfBooks"> <jsonpath headerName="books" resultType="int">USD..store.book.length()</jsonpath> </transform> <to uri="mock:result"/> </route> 189.13. Dependencies To use JSonPath in your camel routes you need to add the a dependency on camel-jsonpath which implements the JSonPath language. If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions). <dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-jsonpath</artifactId> <version>x.x.x</version> </dependency>
from("queue:books.new") .choice() .when().jsonpath("USD.store.book[?(@.price < 10)]") .to("jms:queue:book.cheap") .when().jsonpath("USD.store.book[?(@.price < 30)]") .to("jms:queue:book.average") .otherwise() .to("jms:queue:book.expensive") <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring"> <route> <from uri="direct:start"/> <choice> <when> <jsonpath>USD.store.book[?(@.price &lt; 10)]</jsonpath> <to uri="mock:cheap"/> </when> <when> <jsonpath>USD.store.book[?(@.price &lt; 30)]</jsonpath> <to uri="mock:average"/> </when> <otherwise> <to uri="mock:expensive"/> </otherwise> </choice> </route> </camelContext> USD.store.book[?(@.price < 20)] store.book.price < 20 price < 20 left OP right store.book.price < USD{header.limit} from("direct:start") .choice() // use true to suppress exceptions .when().jsonpath("person.middlename", true) .to("mock:middle") .otherwise() .to("mock:other"); <route> <from uri="direct:start"/> <choice> <when> <jsonpath suppressExceptions="true">person.middlename</jsonpath> <to uri="mock:middle"/> </when> <otherwise> <to uri="mock:other"/> </otherwise> </choice> </route> from("direct:start") .choice() .when().jsonpath("USD.store.book[?(@.price < USD{header.cheap})]") .to("mock:cheap") .when().jsonpath("USD.store.book[?(@.price < USD{header.average})]") .to("mock:average") .otherwise() .to("mock:expensive"); <route> <from uri="direct:start"/> <choice> <when> <jsonpath>USD.store.book[?(@.price < USD{header.cheap})]</jsonpath> <to uri="mock:cheap"/> </when> <when> <jsonpath>USD.store.book[?(@.price < USD{header.average})]</jsonpath> <to uri="mock:average"/> </when> <otherwise> <to uri="mock:expensive"/> </otherwise> </choice> </route> .when().jsonpath("USD.store.book[?(@.price < 10)]", false, false) <jsonpath allowSimple="false">USD.store.book[?(@.price < 10)]</jsonpath> public class Foo { @Consume(uri = "activemq:queue:books.new") public void doSomething(@JsonPath("USD.store.book[*].author") String author, @Body String json) { // process the inbound message here } } from("direct:start") .split().jsonpath("USD.store.book[*]") .to("log:book"); from("direct:start") .split().jsonpathWriteAsString("USD.store.book[*]") .to("log:book"); from("direct:start") .setHeader("numberOfBooks") .jsonpath("USD..store.book.length()", false, int.class, "books") .to("mock:result"); <route> <from uri="direct:start"/> <setHeader headerName="numberOfBooks"> <jsonpath headerName="books" resultType="int">USD..store.book.length()</jsonpath> </transform> <to uri="mock:result"/> </route> <dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-jsonpath</artifactId> <version>x.x.x</version> </dependency>