Chapter 179. JsonPath Language

The JsonPath language supports 7 options which are listed below.

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>$.store.book[?(@.price &lt; 10)]</jsonpath>
        <to uri="mock:cheap"/>
      </when>
      <when>
        <jsonpath>$.store.book[?(@.price &lt; 30)]</jsonpath>
        <to uri="mock:average"/>
      </when>
      <otherwise>
        <to uri="mock:expensive"/>
      </otherwise>
    </choice>
  </route>
</camelContext>

See the JSonPath project page for further examples.

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

$.store.book[?(@.price < 20)]

However what if you could just write it as

store.book.price < 20

And you can omit the path if you just want to look at nodes with a price key

price < 20

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 $ sign, and only include one operator.

The easy syntax is:

left OP right

You can use Camel simple language in the right operator, eg

store.book.price < ${header.limit}

Camel JSonPath supports message body using the following types:

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)

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.

Available as of Camel 2.18

Its now possible to inlined Simple language expressions in the JSonPath expression using the simple syntax ${xxx}. An example is shown below:

from("direct:start")
  .choice()
    .when().jsonpath("$.store.book[?(@.price < ${header.cheap})]")
      .to("mock:cheap")
    .when().jsonpath("$.store.book[?(@.price < ${header.average})]")
      .to("mock:average")
    .otherwise()
      .to("mock:expensive");

And in XML DSL:

<route>
  <from uri="direct:start"/>
  <choice>
    <when>
      <jsonpath>$.store.book[?(@.price < ${header.cheap})]</jsonpath>
      <to uri="mock:cheap"/>
    </when>
    <when>
      <jsonpath>$.store.book[?(@.price < ${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("$.store.book[?(@.price < 10)]", false, false)

And in XML DSL:

<jsonpath allowSimple="false">$.store.book[?(@.price < 10)]</jsonpath>

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("$.store.book[*].author") String author, @Body String json) {
      // process the inbound message here
    }
}

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).

You can use jsonpath to split a JSon document, such as:

from("direct:start")
    .split().jsonpath("$.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("$.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.

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("$..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">$..store.book.length()</jsonpath>
  </transform>
  <to uri="mock:result"/>
</route>

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>