JSONPath

Since Camel 2.13

Camel supports JSONPath to allow using Expression or Predicate on JSON messages.

JSONPath Options

The JSONPath language supports 9 options, which are listed below.

Name Default Java Type Description

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.

unpackArray

false

Boolean

Whether to unpack a single element json-array into an object.

option

Enum

To configure additional options on JSONPath. Multiple values can be separated by comma.

Enum values:

  • DEFAULT_PATH_LEAF_TO_NULL

  • ALWAYS_RETURN_LIST

  • AS_PATH_LIST

  • SUPPRESS_EXCEPTIONS

  • REQUIRE_PROPERTIES

source

String

Source to use, instead of message body. You can prefix with variable:, header:, or property: to specify kind of source. Otherwise, the source is assumed to be a variable. Use empty or null to use default source, which is the message body.

resultType

String

Sets the class of the result type (type from output).

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

Examples

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

  • Java

  • XML DSL

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");
<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>

JSONPath Syntax

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)]

Easy JSONPath Syntax

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 defined 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}

See the JSONPath project page for more syntax examples.

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 a 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)

Suppressing exceptions

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:

  • Java

  • XML DSL

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>

This option is also available on the @JsonPath annotation.

Inline Simple expressions

It’s possible to inlined Simple language in the JSONPath expression using the simple syntax ${xxx}.

An example is shown below:

  • Java

  • XML DSL

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

  • Java

  • XML DSL

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

JSONPath injection

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
    }
}

Encoding Detection

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.

Split JSON data into sub rows as JSON

You can use JSONPath to split a JSON document, such as:

from("direct:start")
    .split().jsonpath("$.store.book[*]", List.class)
    .to("log:book");
Notice how we specify List.class as the result-type. This is because if there is only a single element (only 1 book), then jsonpath will return the single entity as a Map instead of List<Map>. Therefore, we tell Camel that the result should always be a List, and Camel will then automatic wrap the single element into a new List object.

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[*]", List.class)
    .to("log:book");

Then each book is logged as a String JSON value.

Unpack a single-element array into an object

It is possible to unpack a single-element array into an object:

from("direct:start")
    .setBody().jsonpathUnpack("$.store.book", Book.class)
    .to("log:book");

If a book array contains only one book, it will be converted into a Book object.

Using header as input

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>

Transforming a JSon message

For basic JSon transformation where you have a fixed structure, you can represent with a combination of using Camel simple and JSonPath language as:

{
  "company": "${jsonpath($.customer.name)}",
  "location": "${jsonpath($.customer.address.country)}",
  "gold": ${jsonpath($.customer.orders.length() > 5)}
}

Here we use the simple language to define the structure and use JSonPath as inlined functions via the ${jsonpath(exp)} syntax.

This makes it possible to use simple as a template language to define a basic structure and then JSonPath to grab the data from an incoming JSon message. The output of the transformation is also JSon, but with simple you could also make it XML or plain text based:

<customer gold="${jsonpath($.customer.orders.length() > 5)}">
    <company>${jsonpath($.customer.name)}</company>
    <location>${jsonpath($.customer.address.country)}</location>
</customer>

Spring Boot Auto-Configuration

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>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 9 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

Whether to enable auto configuration of the jsonpath language. This is enabled by default.

Boolean

camel.language.jsonpath.option

To configure additional options on JSONPath. Multiple values can be separated by comma.

String

camel.language.jsonpath.source

Source to use, instead of message body. You can prefix with variable:, header:, or property: to specify kind of source. Otherwise, the source is assumed to be a variable. Use empty or null to use default source, which is 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.unpack-array

Whether to unpack a single element json-array into an object.

false

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
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