Tag Archives: jackson

JSON Parsers


JSON (JavaScript Object Notation) is most popular for NoSQL data storage, data exchange format between browsers and web servers and latest framework also use for communication over networks.

For Example :

  • All latest browsers natively support parse JSON data to java script to display over page.
  • REST Service support one of MediaType is JSON to exchange data between browsers or client application to servers where these REST Services are deploy.
  • Some latest framework like Elasticsearch, Logstash, Kibana, Kafka ,Filebeat etc. are used JSON for internal storage and data exchange over network between servers.

All these above cases, JSON data language independent feature provides communication compatibility between different type frameworks and servers. All these frameworks and servers implemented by one of computer language which provides JSON API’s by internally or consumed third party library for parsing and generation.

Here we will focus mainly on Java based JSON APIs which provide various choices for parsing and JSON generation on different cases from JAVA objects.

The Java Open Source Community developed some JSON APIs which offers more choices and flexibility to work with JSON. Here is list of some well-known JSON APIS:

  • Jackson
  • GSON
  • Boon
  • JSON.org

See also : Serialization and Deserialization of JSON to/from JAVA.

JACKSON

Jackson is most popular Java JSON APIs which provide several choices to work with JSON. It contains two different parsers:

  • JsonParser : This is pull parser, which parse one token at a time. These token generated by JsonGenerator.
  • JsonMapper : This parser is use convert customize JSON to/from JAVA object. It also parse data in tree model.

You can follow this link to more detail about Jackson JSON APIs : https://github.com/FasterXML/jackson

GSON

GSON provides flexible Java JSON API developed by Google. GSON APIs are able to work with arbitrary Java objects including pre-existing objects that you do not have source code. It also supports for handling complex objects with generics and deep inheritance. GSON is having three different parsers for JSON Java APIS:

  • Gson class : It can parse JSON into custom Java objects.
  • JsonReador : It’s pull JSON parser, which parse one token at a time.
  • JsonParser : It’s parser JSON into a tree structure of GSON specific Java Objects.

You can follow this link to more detail about GSON JSON APIs : https://github.com/google/gson

Boon

Boon is a standard JSON API in Groovy . It is similar to JACKSON but not only apecific for Java JSON API. It’s complete tool kit to working with data, file process and REST services etc. Boon contains the following Java JSON parsers:

  • ObjectMapper :This parser is use to parse JSON into custom objects and Java Maps.

You can follow this link to more detail about BOON JSON APIs : https://github.com/boonproject/boon

JSON.org

JSON.org provides the first JSON API developed for Java. It’s easy to use but not flexible and fast as compared to others  Java JSON open source APIs.

As I recommend if your application is too old and using this API then only go with it otherwise you can switch with others above Java JSON APIs.

You can follow this link to more detail about JSON.org JSON APIs : https://github.com/douglascrockford/JSON-java

Here, In my further posts for JSON I will focus on JACKSON and GSON because that are most known JSON APIs used by developers.

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[Solved] com.fasterxml.jackson.databind.exc. MismatchedInputException: Cannot deserialize instance of `XYZ` out of START_ARRAY token


MismatchedInpuException is base class for all JsonMappingExceptions. It occurred when input is not mapping with target definition or mismatch between as required for fulfilling the deserialization. This exception is used for some input problems, but in most cases, there should be more explicit subtypes to use.

Example of MismatchedInputException

Here MismatchedInpuException issue is happening because of type mismatch because passing JSON as an array of StudentDetail while deserialization is mapped for single StudentDetail object.

public class StudentDetail {
	private int rollNumber;
	private String firstName;
	private String lastName;

	//getter and setter of class
}
import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;

public class TestJacksonExample2 {

	public static void main(String[] args) {
	    String json=" ["
	    				+ "{\"rollNumber\":21 , \"firstName\":\"Saurabh\" , \"lastName\":\"Gupta\"}, "
	    				+ "{\"rollNumber\":22 , \"firstName\":\"Abhishek\" , \"lastName\":\"Garg\"}"
	    		+ "]";

	    System.out.println(json);
		try
		{
	    ObjectMapper mapper = new ObjectMapper();
		//issue is here
	    StudentDetail student= mapper.readValue(json, StudentDetail.class);
	    System.out.println(student);
		}
		catch(IOException ex)
		{
			ex.printStackTrace();
		}
		catch(Exception ex)
		{
			ex.printStackTrace();
		}

	}

}

MismatchedInputException Stacktrace


 [{"rollNumber":21 , "firstName":"Saurabh" , "lastName":"Gupta"}, {"rollNumber":22 , "firstName":"Abhishek" , "lastName":"Garg"}]
com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `com.fiot.json.jackson.exceptions.StudentDetail` out of START_ARRAY token
 at [Source: (String)" [{"rollNumber":21 , "firstName":"Saurabh" , "lastName":"Gupta"}, {"rollNumber":22 , "firstName":"Abhishek" , "lastName":"Garg"}]"; line: 1, column: 2]
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1343)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1139)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1093)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromArray(BeanDeserializerBase.java:1461)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:185)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:161)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4013)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3004)
    at com.fiot.json.jackson.exceptions.TestJacksonExample2.main(TestJacksonExample2.java:22)

Solutions

To resolve this issue, change the type from StudentDetail to as array StudentDetail[]

public static void main(String[] args) {
	    String json=" ["
	    				+ "{\"rollNumber\":21 , \"firstName\":\"Saurabh\" , \"lastName\":\"Gupta\"}, "
	    				+ "{\"rollNumber\":22 , \"firstName\":\"Abhishek\" , \"lastName\":\"Garg\"}"
	    		+ "]";
	    System.out.println(json);
		try
		{
	    ObjectMapper mapper = new ObjectMapper();
		//Convereted to Type as array
	    StudentDetail[] students= mapper.readValue(json,  StudentDetail[].class );
	    System.out.println(students);
		}
		catch(IOException ex)
		{
			ex.printStackTrace();
		}
		catch(Exception ex)
		{
			ex.printStackTrace();
		}

	}

References

https://fasterxml.github.io/jackson-databind/javadoc/2.9/com/fasterxml/jackson/databind/exc/MismatchedInputException.html

You would like to see

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How to retrieve key Information from JSON Data?


Jackson provide API’s to parse information based on Key  name.  It’s work like DOM parser and make tree of properties in JSON. Based on Path,Jackson retrieve this information for keys.

Pre-Requisite 

Add below jackson-databind-2.8.5.jar in your classpath or make dependency entry in pom.xml file.

  <dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.8.5</version>
  </dependency>
 

Example

In below example we have some sample JSON Data for Student and by Jackson API will try to retrieve keys information like rollNumber and phoneNumbers.

Sample DATA

{
"rollNumber" : 11,
"firstName" : "Saurabh",
"lastName" : "Gupta",
"permanent" : false,
"address" : {
"addressLine" : "Lake Union Hill Way",
"city" : "Atlanta",
"zipCode" : 50005
},
"phoneNumbers" : [ 2233445566, 3344556677 ],
"cities" : [ "Dallas", "San Antonio", "Irving" ],
"properties" : {
"play" : "Badminton",
"interst" : "Math",
"age" : "34 years"
}
}

Sample Code

package test.facingissesonit.json.jacson;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Iterator;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class ReadJsonByKeyName {

	public static void main(String[] args) {
		try
		{
		byte[] jsonData = Files.readAllBytes(Paths.get("student_data2.txt"));

		ObjectMapper objectMapper = new ObjectMapper();

		//Jacson read JSON like DOM Parser and create tree of properties
		JsonNode rootNode = objectMapper.readTree(jsonData);

		JsonNode idNode = rootNode.path("rollNumber");
		System.out.println("rollNumber = "+idNode.asInt());

		JsonNode phoneNosNode = rootNode.path("phoneNumbers");
		Iterator<JsonNode> elements = phoneNosNode.elements();
		while(elements.hasNext()){
			JsonNode phone = elements.next();
			System.out.println("Phone No = "+phone.asLong());
		}
		}
		catch(JsonProcessingException ex)
		{
			ex.printStackTrace();
		}
		catch(IOException ex)
		{
			ex.printStackTrace();
		}
	}
}

Output

rollNumber = 11
Phone No = 2233445566
Phone No = 3344556677

More Sample Code

For more java and JDBC codes follow below links

How to create dynamic JSON by Java?


Jackson  provide Java api’s   to create JSON on runtime . These api’s can handle different type of data and objects.

Jacson API’s

Writing Root Object
JsonGenerator.writeStartObject();
JsonGenerator.writeEndObject();

Writing Sub Object
JsonGenerator.writeObjectFieldStart();
JsonGenerator.writeEndObject();

Writing Array
JsonGenerator.writeArrayFieldStart()
JsonGenerator.writeEndObject();

Writing Field Level
JsonGenerator.writeNumberField();
JsonGenerator.writeStringField();
JsonGenerator.writeBooleanField();

Pre-Requisite 

Add below jackson-databind-2.8.5.jar in your classpath or make dependency entry in pom.xml file.

  <dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.8.5</version>
  </dependency>
 

Example

In below example by Jacson API’s generating JSON on runtime and writing on file.

package test.facingissesonit.json.jacson;

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;

public class JsonStreamWriteToFile {

	public static void main(String[] args) {
		Student student = sampleStudentObject();
		try {
			JsonGenerator jsonGenerator = new JsonFactory().createGenerator(new FileOutputStream("student_data.txt"));
			// for pretty formatted printing
			jsonGenerator.setPrettyPrinter(new DefaultPrettyPrinter());
			// start root from here
			jsonGenerator.writeStartObject();

			jsonGenerator.writeNumberField("rollNumber", student.getRollNumber());
			jsonGenerator.writeStringField("firstName", student.getFirstName());
			jsonGenerator.writeStringField("lastName", student.getLastName());
			jsonGenerator.writeBooleanField("permanent", student.isPermanent());

			jsonGenerator.writeObjectFieldStart("address"); // object writing
			jsonGenerator.writeStringField("addressLine", student.getAddress().getAddressLine());
			jsonGenerator.writeStringField("city", student.getAddress().getCity());
			jsonGenerator.writeNumberField("zipCode", student.getAddress().getZipCode());
			jsonGenerator.writeEndObject(); // address object completed

			jsonGenerator.writeArrayFieldStart("phoneNumbers");
			for (long num : student.getPhoneNumbers())
				jsonGenerator.writeNumber(num);
			jsonGenerator.writeEndArray();

			 // start array writing for cities
			jsonGenerator.writeArrayFieldStart("cities");
			for (String city : student.getCities())
				jsonGenerator.writeString(city);
			// closing cities array
			jsonGenerator.writeEndArray(); 

			jsonGenerator.writeObjectFieldStart("properties");
			Set<String> keySet = student.getProperties().keySet();
			for (String key : keySet) {
				String value = student.getProperties().get(key);
				jsonGenerator.writeStringField(key, value);
			}
			// End of  properties writing
			jsonGenerator.writeEndObject();
			//End root object writing
			jsonGenerator.writeEndObject(); 

			jsonGenerator.flush();
			jsonGenerator.close();

		} catch (IOException ex) {
			ex.printStackTrace();
		}

	}

	public static Student sampleStudentObject() {

		Student student = new Student();
		student.setRollNumber(11);
		student.setFirstName("Saurabh");
		student.setLastName("Gupta");
		student.setPhoneNumbers(new long[] { 2233445566L, 3344556677L });

		Address add = new Address();
		add.setAddressLine("Lake Union Hill Way");
		add.setCity("Atlanta");
		add.setState("GA");
		add.setZipCode(50005);
		student.setAddress(add);

		List<String> cities = new ArrayList<String>();
		cities.add("Dallas");
		cities.add("San Antonio");
		cities.add("Irving");
		student.setCities(cities);

		Map<String, String> props = new HashMap<String, String>();
		props.put("age", "34 years");
		props.put("interst", "Math");
		props.put("play", "Badminton");

		student.setProperties(props);

		return student;
	}
}

Model Object

Student and Address classes are required to execute these code

package test.facingissesonit.json.jacson;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Student {
	private int rollNumber;
	private String firstName;
	private String lastName;
	private boolean permanent;
	private Address address;
	private long[] phoneNumbers;
	private List<String> cities;
	private Map<String, String> properties;
	@Override
	public String toString()
	{
		StringBuffer sb=new StringBuffer();
		sb.append("==============Student Information================\n");
		sb.append("rollNumber=").append(rollNumber).append("\n");
		sb.append("firstName=").append(firstName).append("\n");
		sb.append("lastName=").append(lastName).append("\n");
		sb.append("permanent=").append(permanent).append("\n");
		sb.append("adress=").append(address).append("\n");
		sb.append("phoneNumbers=").append(Arrays.toString(phoneNumbers)).append("\n");
		sb.append("cities=").append(Arrays.toString(cities.toArray(new String[cities.size()]))).append("\n");
		sb.append("properties=").append(properties).append("\n");
		return sb.toString();
	}
	public int getRollNumber() {
		return rollNumber;
	}
	public void setRollNumber(int rollNumber) {
		this.rollNumber = rollNumber;
	}
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	public boolean isPermanent() {
		return permanent;
	}
	public void setPermanent(boolean permanent) {
		this.permanent = permanent;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	public long[] getPhoneNumbers() {
		return phoneNumbers;
	}
	public void setPhoneNumbers(long[] phoneNumbers) {
		this.phoneNumbers = phoneNumbers;
	}
	public List<String> getCities() {
		return cities;
	}
	public void setCities(List<String> cities) {
		this.cities = cities;
	}
	public Map<String, String> getProperties() {
		return properties;
	}
	public void setProperties(Map<String, String> properties) {
		this.properties = properties;
	}

}

package test.facingissesonit.json.jacson;

public class Address {
private String addressLine;
private String city;
private String state;
private int zipCode;
@Override
public String toString()
{
	StringBuffer sb=new StringBuffer();
	sb.append("AddressLine=").append(addressLine).append("\n");
	sb.append("city=").append(city).append("\n");
	sb.append("state=").append(state).append("\n");
	sb.append("zipCode=").append(zipCode).append("\n");
	return sb.toString();
}
public String getAddressLine() {
	return addressLine;
}
public void setAddressLine(String addressLine) {
	this.addressLine = addressLine;
}
public String getCity() {
	return city;
}
public void setCity(String city) {
	this.city = city;
}
public String getState() {
	return state;
}
public void setState(String state) {
	this.state = state;
}
public int getZipCode() {
	return zipCode;
}
public void setZipCode(int zipCode) {
	this.zipCode = zipCode;
}
}

Output

Generated output on Student_data.txt file

{
  "rollNumber" : 11,
  "firstName" : "Saurabh",
  "lastName" : "Gupta",
  "permanent" : false,
  "address" : {
    "addressLine" : "Lake Union Hill Way",
    "city" : "Atlanta",
    "zipCode" : 50005
  },
  "phoneNumbers" : [ 2233445566, 3344556677 ],
  "cities" : [ "Dallas", "San Antonio", "Irving" ],
  "properties" : {
    "play" : "Badminton",
    "interst" : "Math",
    "age" : "34 years"
  }
}

More Sample Code

For more java and JDBC codes follow below links

How to Convert JSON data from file to ArrayList?


Jackson provide api’s  to convert JSON data to Collections Objects like Map, ArrayList etc.

In below example file student_data.txt having collections of students data in JSON form and through these Jacson API’s will convert JSON data to ArrayList java object.

Pre-Requisite 

Add below jackson-databind-2.8.5.jar in your classpath or make dependency entry in pom.xml file.

  <dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.8.5</version>
  </dependency>
 

Sample Data

 Add below content in  student_data.txt

[
{
  "rollNumber" : 11,
  "firstName" : "Saurabh",
  "lastName" : "Gupta",
  "permanent" : false,
  "address" : {
    "addressLine" : "Lake Union Hill Way",
    "city" : "Atlanta",
    "zipCode" : 50005
  },
  "phoneNumbers" : [ 2233445566, 3344556677 ],
  "cities" : [ "Dallas", "San Antonio", "Irving" ],
  "properties" : {
    "play" : "Badminton",
    "interst" : "Math",
    "age" : "34 years"
  }
},
{
  "rollNumber" : 11,
  "firstName" : "Gaurav",
  "lastName" : "Khaira",
  "permanent" : true,
  "address" : {
    "addressLine" : " 5770 Shiloh woods dr",
    "city" : "Cumming",
    "zipCode" : 50007
  },
  "phoneNumbers" : [ 2233445567, 3344556678 ],
  "cities" : [ "New York", "Austin", "Plano" ],
  "properties" : {
    "play" : "Baseball",
    "interst" : "Science",
    "age" : "36 years"
  }
}
]

 

Example 

package test.facingissesonit.json.jacson;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;

import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class ConvertJsonToArrayList {

	public static void main(String[] args) {
		try
		{
		byte[] mapData = Files.readAllBytes(Paths.get("student_data.txt"));
		Student[] studentArr = null;

		ObjectMapper objectMapper = new ObjectMapper();
		studentArr = objectMapper.readValue(mapData, Student[].class);
		List<Student> studentList=Arrays.asList(studentArr);
		System.out.println("Student 1 \n"+studentList.get(0));
		System.out.println("Student 2 \n"+studentList.get(1));

		}
		catch(JsonMappingException ex)
		{
			ex.printStackTrace();
		}
		catch(IOException ex)
		{
			ex.printStackTrace();
		}
	}
}

 

Model Classes

Below Student and Address are required classes for execute this code.

package test.facingissesonit.json.jacson;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Student {
	private int rollNumber;
	private String firstName;
	private String lastName;
	private boolean permanent;
	private Address address;
	private long[] phoneNumbers;
	private List<String> cities;
	private Map<String, String> properties;
	@Override
	public String toString()
	{
		StringBuffer sb=new StringBuffer();
		sb.append("==============Student Information================\n");
		sb.append("rollNumber=").append(rollNumber).append("\n");
		sb.append("firstName=").append(firstName).append("\n");
		sb.append("lastName=").append(lastName).append("\n");
		sb.append("permanent=").append(permanent).append("\n");
		sb.append("adress=").append(address).append("\n");
		sb.append("phoneNumbers=").append(Arrays.toString(phoneNumbers)).append("\n");
		sb.append("cities=").append(Arrays.toString(cities.toArray(new String[cities.size()]))).append("\n");
		sb.append("properties=").append(properties).append("\n");
		return sb.toString();
	}
	public int getRollNumber() {
		return rollNumber;
	}
	public void setRollNumber(int rollNumber) {
		this.rollNumber = rollNumber;
	}
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	public boolean isPermanent() {
		return permanent;
	}
	public void setPermanent(boolean permanent) {
		this.permanent = permanent;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	public long[] getPhoneNumbers() {
		return phoneNumbers;
	}
	public void setPhoneNumbers(long[] phoneNumbers) {
		this.phoneNumbers = phoneNumbers;
	}
	public List<String> getCities() {
		return cities;
	}
	public void setCities(List<String> cities) {
		this.cities = cities;
	}
	public Map<String, String> getProperties() {
		return properties;
	}
	public void setProperties(Map<String, String> properties) {
		this.properties = properties;
	}

}

package test.facingissesonit.json.jacson;

public class Address {
private String addressLine;
private String city;
private String state;
private int zipCode;
@Override
public String toString()
{
	StringBuffer sb=new StringBuffer();
	sb.append("AddressLine=").append(addressLine).append("\n");
	sb.append("city=").append(city).append("\n");
	sb.append("state=").append(state).append("\n");
	sb.append("zipCode=").append(zipCode).append("\n");
	return sb.toString();
}
public String getAddressLine() {
	return addressLine;
}
public void setAddressLine(String addressLine) {
	this.addressLine = addressLine;
}
public String getCity() {
	return city;
}
public void setCity(String city) {
	this.city = city;
}
public String getState() {
	return state;
}
public void setState(String state) {
	this.state = state;
}
public int getZipCode() {
	return zipCode;
}
public void setZipCode(int zipCode) {
	this.zipCode = zipCode;
}
}

Output

Below is console output generated by program which is from Java Object.

Student 1
==============Student Information================
rollNumber=11
firstName=Saurabh
lastName=Gupta
permanent=false
adress=AddressLine=Lake Union Hill Way
city=Atlanta
state=null
zipCode=50005

phoneNumbers=[2233445566, 3344556677]
cities=[Dallas, San Antonio, Irving]
properties={play=Badminton, interst=Math, age=34 years}

Student 2
==============Student Information================
rollNumber=11
firstName=Gaurav
lastName=Khaira
permanent=true
adress=AddressLine= 5770 Shiloh woods dr
city=Cumming
state=null
zipCode=50007

phoneNumbers=[2233445567, 3344556678]
cities=[New York, Austin, Plano]
properties={play=Baseball, interst=Science, age=36 years}

More Sample Code

For more java and JDBC codes follow below links

Elasticsearch REST JAVA Client to get Index Details List


Below is example to get Index Detail in Java Array by using Elasticsearch REST Java client. Here client will call endpoint  “/_cat/indices?format=json” to retrieve all detail of index list. It is same as we use GET by CURL

GET http://elasticsearchHost:9200/_cat/indices?format=json
 

Pre-requisite

  • Minimum requirement for Java 7 version required.
  • Add below dependency for Elasticsearch REST and JSON Mapping in your pom.xml or add in your class path.

Dependency

<!--Elasticsearch REST jar-->
<dependency>
			<groupId>org.elasticsearch.client</groupId>
			<artifactId>rest</artifactId>
			<version>5.1.2</version>
</dependency>
<!--Jackson jar for mapping json to Java -->
<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.8.5</version>
</dependency>

Sample Code

import java.io.IOException;
import java.util.Collections;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.elasticsearch.client.Response;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;

import com.fasterxml.jackson.databind.ObjectMapper;

public class ElasticsearchRESTIndexClient {

	public static void main(String[] args) {
		IndexInfo []indexArr = null;
		RestClient client = null;
		try {
			client = openConnection();
			if (client != null) {
				// performRequest GET method will retrieve all index detail list
				// information from elastic server
				Response response = client.performRequest("GET", "/_cat/indices?format=json",
						Collections.singletonMap("pretty", "true"));
				// GetEntity api will return content of response in form of json
				// in Http Entity
				HttpEntity entity = response.getEntity();
				ObjectMapper jacksonObjectMapper = new ObjectMapper();
				// Map json response to Java object in IndexInfo Array
				// Cluster Info
				indexArr = jacksonObjectMapper.readValue(entity.getContent(), IndexInfo[].class);
				for(IndexInfo indexInfo:indexArr)
				{
				System.out.println(indexInfo);
			    }
			}

		} catch (Exception ex) {
			System.out.println("Exception found while getting cluster detail");
			ex.printStackTrace();
		} finally {
			closeConnnection(client);
		}

	}

	// Get Rest client connection
	private static RestClient openConnection() {
		RestClient client = null;
		try {
			final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
			credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("userid", "password"));
			client = RestClient.builder(new HttpHost("elasticHost", Integer.parseInt("9200")))
					.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
						// Customize connection as per requirement
						public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
							return httpClientBuilder
									// Credentials
									.setDefaultCredentialsProvider(credentialsProvider)
									// Proxy
									.setProxy(new HttpHost("proxyServer", 8080));

						}
					}).setMaxRetryTimeoutMillis(60000).build();

		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return client;
	}

	// Close Open connection
	private static void closeConnnection(RestClient client) {
		if (client != null) {
			try {
				client.close();
			} catch (IOException ex) {
				ex.printStackTrace();
			}
		}
	}

}

Index Info Object where JSON index detail will map

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;

@JsonIgnoreProperties(ignoreUnknown = true)
public class IndexInfo {
@JsonProperty(value = "health")
private String health;
@JsonProperty(value = "index")
private String indexName;
@JsonProperty(value = "status")
private String status;
@JsonProperty(value = "pri")
private int shards;
@JsonProperty(value = "rep")
private int replica;
@JsonProperty(value = "pri.store.size")
private String dataSize;
@JsonProperty(value = "store.size")
private String totalDataSize;
@JsonProperty(value = "docs.count")
private String documentCount;

@Override
public String toString()
{
	StringBuffer str=new StringBuffer(60);
	str.append("{\n");
	str.append("    \"").append("indexName").append("\":\"").append(indexName).append("\",\n");
	str.append("    \"").append("health").append("\":\"").append(health).append("\",\n");
	str.append("    \"").append("status").append("\":\"").append(status).append("\",\n");
	str.append("    \"").append("shards").append("\":\"").append(shards).append("\",\n");
	str.append("    \"").append("replica").append("\":\"").append(replica).append("\",\n");
	str.append("    \"").append("dataSize").append("\":\"").append(dataSize).append("\",\n");
	str.append("    \"").append("totalDataSize").append("\":\"").append(totalDataSize).append("\",\n");
	str.append("    \"").append("documentCount").append("\":\"").append(documentCount).append("\"\n");
	str.append("    \"");
	return str.toString();
}
public String getIndexName() {
	return indexName;
}
public void setIndexName(String indexName) {
	this.indexName = indexName;
}
public int getShards() {
	return shards;
}
public void setShards(int shards) {
	this.shards = shards;
}
public int getReplica() {
	return replica;
}
public void setReplica(int replica) {
	this.replica = replica;
}
public String getDataSize() {
	return dataSize;
}
public void setDataSize(String dataSize) {
	this.dataSize = dataSize;
}
public String getTotalDataSize() {
	return totalDataSize;
}
public void setTotalDataSize(String totalDataSize) {
	this.totalDataSize = totalDataSize;
}
public String getDocumentCount() {
	return documentCount;
}
public void setDocumentCount(String documentCount) {
	this.documentCount = documentCount;
}
public String getStatus() {
	return status;
}
public void setStatus(String status) {
	this.status = status;
}
public String getHealth() {
	return health;
}
public void setHealth(String health) {
	this.health = health;
}
}

Read More on Elasticsearch REST

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Elasticsearch REST JAVA Client for Cluster Detail


Below is example to get Cluster Detail in Java Object by using Elasticsearch REST Java client. Here client will call endpoint  “/_cluster/health” to retrieve all detail of index list. It is same as we use GET by CURL

GET http://elasticsearchHost:9200/_cluster/health

Pre-requisite

  • Minimum requirement for Java 7 version required.
  • Add below dependency for Elasticsearch REST and JSON Mapping in your pom.xml or add in your class path.

Dependency

<!--Elasticsearch REST jar-->
<dependency>
			<groupId>org.elasticsearch.client</groupId>
			<artifactId>rest</artifactId>
			<version>5.1.2</version>
</dependency>
<!--Jackson jar for mapping json to Java -->
<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.8.5</version>
</dependency>

Sample Code

import java.io.IOException;
import java.util.Collections;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.elasticsearch.client.Response;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;

import com.fasterxml.jackson.databind.ObjectMapper;

public class ElasticsearchRESTClusterClient {

	public static void main(String[] args) {
		ClusterInfo clusterHealth = null;
		RestClient client = null;
		try {
			client = openConnection();
			if (client != null) {
				// performRequest GET method will retrieve all cluster health
				// information from elastic server
				Response response = client.performRequest("GET", "/_cluster/health",
						Collections.singletonMap("pretty", "true"));
				// GetEntity api will return content of response in form of json
				// in Http Entity
				HttpEntity entity = response.getEntity();
				ObjectMapper jacksonObjectMapper = new ObjectMapper();
				// Map json response to Java object in ClusterInfo
				// Cluster Info
				clusterHealth = jacksonObjectMapper.readValue(entity.getContent(), ClusterInfo.class);
				System.out.println(clusterHealth);
			}

		} catch (Exception ex) {
			System.out.println("Exception found while getting cluster detail");
			ex.printStackTrace();
		} finally {
			closeConnnection(client);
		}

	}

	// Get Rest client connection
	private static RestClient openConnection() {
		RestClient client = null;
		try {
			final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
			credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("userId", "password"));
			client = RestClient.builder(new HttpHost("elasticHost", Integer.parseInt("9200")))
					.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
						// Customize connection as per requirement
						public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
							return httpClientBuilder
									// Credentials
									.setDefaultCredentialsProvider(credentialsProvider)
									// Proxy
									.setProxy(new HttpHost("ProxyServer", 8080));

						}
					}).setMaxRetryTimeoutMillis(60000).build();

		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return client;
	}

	// Close Open connection
	private static void closeConnnection(RestClient client) {
		if (client != null) {
			try {
				client.close();
			} catch (IOException ex) {
				ex.printStackTrace();
			}
		}
	}

}

Cluster Info Java Object where retrieve json response will map.

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;

@JsonIgnoreProperties(ignoreUnknown = true)
public class ClusterInfo {

@JsonProperty(value = "cluster_name")
private String clusterName;
@JsonProperty(value = "status")
private String clusterStatus;
@JsonProperty(value = "active_primary_shards")
private int primaryActiveShards;
@JsonProperty(value = "active_shards")
private int activeShards;
@JsonProperty(value = "delayed_unassigned_shards")
private int delayedUnAssignedShards;
@JsonProperty(value = "unassigned_shards")
private int unAssignedShards;
@JsonProperty(value = "initializing_shards")
private int initializingShards;
@JsonProperty(value = "relocating_shards")
private int relocatingShards;
@JsonProperty(value = "number_of_nodes")
private int totalNodeCount;
@JsonProperty(value = "number_of_data_nodes")
private int dataNodeCount;

@Override
public String toString()
{
	StringBuffer str=new StringBuffer(60);
	str.append("{\n");
	str.append("    \"").append("clusterName").append("\":\"").append(clusterName).append("\",\n");
	str.append("    \"").append("clusterStatus").append("\":\"").append(clusterStatus).append("\",\n");
	str.append("    \"").append("primaryActiveShards").append("\":\"").append(primaryActiveShards).append("\",\n");
	str.append("    \"").append("activeShards").append("\":\"").append(activeShards).append("\",\n");
	str.append("    \"").append("delayedUnAssignedShards").append("\":\"").append(delayedUnAssignedShards).append("\",\n");
	str.append("    \"").append("unAssignedShards").append("\":\"").append(unAssignedShards).append("\",\n");
	str.append("    \"").append("initializingShards").append("\":\"").append(initializingShards).append("\",\n");
	str.append("    \"").append("relocatingShards").append("\":\"").append(relocatingShards).append("\",\n");
	str.append("    \"").append("totalNodeCount").append("\":\"").append(totalNodeCount).append("\",\n");
	str.append("    \"").append("dataNode").append("\":\"").append(dataNodeCount).append("\"");
	str.append("    \"");
	return str.toString();
}

public String getClusterName() {
	return clusterName;
}
public void setClusterName(String clusterName) {
	this.clusterName = clusterName;
}
public String getClusterStatus() {
	return clusterStatus;
}
public void setClusterStatus(String clusterStatus) {
	this.clusterStatus = clusterStatus;
}
public int getPrimaryActiveShards() {
	return primaryActiveShards;
}
public void setPrimaryActiveShards(int primaryActiveShards) {
	this.primaryActiveShards = primaryActiveShards;
}
public int getActiveShards() {
	return activeShards;
}
public void setActiveShards(int activeShards) {
	this.activeShards = activeShards;
}
public int getDelayedUnAssignedShards() {
	return delayedUnAssignedShards;
}
public void setDelayedUnAssignedShards(int delayedUnAssignedShards) {
	this.delayedUnAssignedShards = delayedUnAssignedShards;
}
public int getUnAssignedShards() {
	return unAssignedShards;
}
public void setUnAssignedShards(int unAssignedShards) {
	this.unAssignedShards = unAssignedShards;
}
public int getInitializingShards() {
	return initializingShards;
}
public void setInitializingShards(int initializingShards) {
	this.initializingShards = initializingShards;
}
public int getRelocatingShards() {
	return relocatingShards;
}
public void setRelocatingShards(int relocatingShards) {
	this.relocatingShards = relocatingShards;
}
public int getDataNodeCount() {
	return dataNodeCount;
}
public void setDataNodeCount(int dataNodeCount) {
	this.dataNodeCount = dataNodeCount;
}
public int getTotalNodeCount() {
	return totalNodeCount;
}
public void setTotalNodeCount(int totalNodeCount) {
	this.totalNodeCount = totalNodeCount;
}
}

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