Overview
In my
last blog, I talked about how
we can use Spring-Data-Elasticsearch project to connect
with Elasticsearch Engine and do all CRUD operations.
However, I did also mention that this project is not updated to be compatible
with latest version of elasticsearch engine. So, In this blog, I am going to
cover how to interact with latest version of elasticsearch engine using Transport
Client library. I am going to use Spring Boot as Client
application and then add dependencies for other required libraries.
Pre-requisites
- Jdk
1.8
- Maven
- Elasticsearch
engine download 5.x or 6.x ( I will explain the steps how to download)
- Eclipse
or VSD as IDE
Setup Elasticsearch
Step 2 -
Select Elasticsearch in drop down and then version as 5.5.0 and click on
Download button.
Step 3 -
It will give you options if you want to download as Zip, TAR, RPM. You can
choose as per your convenience. I selected the Zip format as using it on
windows. Step 4 - unzip the downloaded content and go to
bin folder. There will be a file named elasticsearch.bat.
Step
5 - Run this file on windows OS through command prompt and it will
start the elasticsearch engine for you. Once started, it will start listening
to port 9200. So the url will be http://localhost:9200/ Also, 9300 port
is exposed as cluster node. 9200 port is for REST communication and can
be used by Java or any other language and 9300 is for Elasticsearch Cluster
Node communication with each other as well Java can also connect to this
cluster node using Transport protocol.
Step 6 -
Test to verify if it started properly by launching the url using curl command.
You can use PowerShell on windows.
curl
http://localhost:9200/
Once
the search engine starts up, let's try to test some of the REST apis it
provides to interact with engine.
Launch
- http://localhost:9200/users/employee/1
using Postman or curl with POST method.
Input should be in JSON format.
Response
will show that it has created "users" as index name,
"employee" as type and document has
been created with id as "1".
Now, To
view the content of the document, we can call another REST api end point http://localhost:9200/users/employee/1 using GET method.
This will result the document information as below:
Now, if
we want to search a document by any particular field, you need to add _search as
path in the REST API url. So launch curl -XGET
'http://localhost:9200/users/employee/_search'
This
will search for all the documents for index "users" and type
"employee". Now, if you want to search for a particular field,
need to add Query match criteria as part of JSON.
curl -XGET
'http://localhost:9200/users/employee/_search'
-H
'Content-Type: application/json' -d
'
{"query": { "match": {"name" : "Rajesh"
} }}'
This
will search for a document having field 'name' as 'Rajesh'.
Now, we
have seen how Elasticsearch REST APIs works to create, retrieve and other
operations for the documents; let's try to understand how we can connect to
elasticsearch engine from Applications code. Either, we can make call to these
REST apis directly from the code or we can use Transport Client provided by
Elasticsearch. Let's develop an Spring Boot application to showcase all the
CRUD operations.
Develop Spring Boot
Application
Maven Dependencies
Other
than spring boot jars, It requires elasticsearch, transport client and log4j
jars.
Configuration -
As we
will be using Transport client to connect to elasticsearch engine, we need to
give url path for the cluster node of engine. so i have put properties in
application.properties file for the host and port of
the url.
Domain -
Create
a domain class named User. JSON input will be mapped to this
User object. This will be used to create user document associated with the
index and type.
Configuration -
Java
configuration file has been created to create Transport client which connects
to elasticsearch cluster node. It is also loading the value of host and port
from environment configured through application.properties.
Controller -
UserController is
created to showcase below features -
1. Create
an Index named "users" and Type "employee".
It will create a document storing user information. Id for a document can be
passed as input in JSON or if it is not passed, elasticsearch will generate its
own Id. Client has a method called prepareIndex() which builds
the document object and store against the index and type. This method is a POST
method call where User information will be passed as JSON.
2. View
the user information based on "id" passed. Client has prepareGet()
method to retrieve information based on index, type and id. It will return the
User Information in JSON format.
3. View
the user information based on a field name. I have used matchQuery() here
to search by "name" field and return User information.
However, there are many different types of query() available
with QueryBuilders class . e.g rangeQuery() to
search a field value in particular range like age between 10 to 20 years. There
is a wildcardQuery() to search a field with wildcard. termQuery() is
also available. You can play with all of these based on your need.
4.
Update the document by searching it with Id and replace a
field value. Client has a method called update(). It
accepts UpdateRequest as input which builds the update query.
5. Last
method is to showcase delete a document of an index and type.
Client does have prepareDelete() method which accepts the
index, type and id to delete the document.
Build Application
Run mvn clean
install command to build the jar file.
Start Application
Run java -jar
target/standalone-elasticsearch-0.0.1-SNAPSHOT.jar
command to start the Spring Boot application.
Test Application
Application
will be running on http://localhost:8102
url. Now let's test couple of use cases we talked above.
1. Test
Creating document.
Launch http://localhost:8102/rest/users/create as
POST method either through curl or Postman
Input -
You
will see the response showing "CREATED".
2. To
test if the document has been created, lets test the view functionality.
launch - http://localhost:8102/rest/users/view/1 with
GET method
In
response, you will see the User information for id with value
"1".
3. You
can view User information by name field as well by launching http://localhost:8102/rest/users/view/name/Rajesh
This is passing "Rajesh" as "name" field value.
Similarly,
update and delete features can be tested by launching http://localhost:8102/rest/users/update/1
and http://localhost:8102/rest/users/delete/1
So
these are all the features I have played around and sharing with you through
this blog. As mentioned above, there are many more different types of queries
you can explore with elasticsearch transport client.
