Elasticsearch-Search-Template-Invoking-Java-Client

Elasticsearch Search Template creation on dev tool & Invoke search template in Java client API

Search template

• A search template is a stored search you can run with different variables. If you use Elasticsearch as a search backend, you can pass user input from a search bar as parameters for a search template. This lets you run searches without exposing Elasticsearch’s query syntax to your users. If you use Elasticsearch for a custom application, search templates let you change your searches without modifying your app’s code.

Create a search template

• The request’s source supports the same parameters as the search API's request body. Source also supports Mustache variables which are typically enclosed in double curly brackets: {{my-var}}. When you run a templated search, Elasticsearch replaces these variables with values from params. Search templates must use a lang of mustache. Elasticsearch stores search templates as Mustache scripts in the cluster state. Elasticsearch compiles search templates in the template script context. Settings that limit or disable scripts also affect search templates.
• The following request creates a search template with an id of test-search-template.

PUT _scripts/test-search-template
{
  "script": {
    "lang": "mustache",
    "source": {
      "query": {
        "match": {
          "message": "{{query_string}}"
        }
      },
      "from": "{{from}}",
      "size": "{{size}}"
    },
    "params": {
      "query_string": "Hello Test"
    }
  }
}

Validate a search template

• To test the template with different parameters, use the render search template API.

POST _render/template
{
  "id": "test-search-template",
  "params": {
    "query_string": "Test The Template",
    "from": 20,
    "size": 10
  }
}

Run a templated search

• To run a search with a search template, use the search template API. You can specify different parameters with each request.

GET sample-index/_search/template
{
  "id": "test-search-template",
  "params": {
    "query_string": "Test The Template",
    "from": 0,
    "size": 10
  }
}

Source Code Explanation

• Source code is located in the following path: src\main\java\org\example\src\TextSearchTemplate.java
  • The code demonstrates the usage of the Elasticsearch High-Level REST Client to perform a search using a search template.
  • The code sets up the Elasticsearch client connection by creating a RestClientBuilder instance and specifying the remote server's IP address, port and protocol (HTTP).
  • Credentials are configured using the BasicCredentialsProvider and the provided username and password.
  • The RestHighLevelClient is created using the configured RestClientBuilder.
  • A SearchTemplateRequest object is created to define the search template request.
  • The SearchRequest is set on the SearchTemplateRequest, specifying the index name where the search will be performed.
  • The script type is set to ScriptType.STORED, indicating that the search template is stored on the Elasticsearch server.
  • The name of the search template is set using the setScript method. In our case, it is set to "test-search-template".
  • Template parameters are defined using a HashMap. In the example, the field name and value are specified as parameters.
  • The template parameters are set on the SearchTemplateRequest using the setScriptParams method.
  • The search is executed by calling the client.searchTemplate method, passing the SearchTemplateRequest and default request options.
  • The response is obtained as a SearchTemplateResponse.
  • The search response is extracted from the template response using the getResponse method.
  • The hits (search results) are retrieved from the search response using the getHits method.
  • The code iterates over the hits using a for loop and prints the source of each hit using getSourceAsString.
  • The program handles IOException exceptions that may occur during the execution of the Elasticsearch operations and prints the stack trace if an exception occurs.
  • Finally, the close method is called on the RestHighLevelClient to release resources.