Chapter 74. JSONPath

The JSONPath language supports 8 options, which are listed below.

For example, you can use JSONPath in a Predicate with the Content Based Router EIP.

from("queue:books.new")
  .choice()
    .when().jsonpath("$.store.book[?(@.price < 10)]")
      .to("jms:queue:book.cheap")
    .when().jsonpath("$.store.book[?(@.price < 30)]")
      .to("jms:queue:book.average")
    .otherwise()
      .to("jms:queue:book.expensive");

And in XML DSL:

<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>

Using the JSONPath syntax takes some time to learn, even for basic predicates. So for example to find out all the cheap books you have to do:

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

store.book.price < 20

price < 20

left OP right

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)

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.

It’s possible to inlined Simple language 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 &lt; ${header.cheap})]</jsonpath>
      <to uri="mock:cheap"/>
    </when>
    <when>
      <jsonpath>$.store.book[?(@.price &lt; ${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 &lt; 10)]</jsonpath>

You can use Bean Integration to invoke a method on a bean and use various languages such as JSONPath (via the @JsonPath annotation) to extract a value from the message and bind it to a method parameter, as shown below:

public class Foo {

    @Consume("activemq:queue:books.new")
    public void doSomething(@JsonPath("$.store.book[*].author") String author, @Body String json) {
      // process the inbound message here
    }
}

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 JSONPath, or you can specify the encoding in the header CamelJsonPathJsonEncoding which is defined as a constant in: 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 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.

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 name="numberOfBooks">
    <jsonpath headerName="books" resultType="int">$..store.book.length()</jsonpath>
  </setHeader>
  <to uri="mock:result"/>
</route>

When using jsonpath 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-jsonpath-starter</artifactId>
</dependency>

The component supports 8 options, which are listed below.