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### What is this PR for? **New Java interpreter** There are several Java libraries that could be used to leverage the Data Visualization & Collaboration features of Zeppelin hence the need of a Java interpreter to run any java code / library with no further dependencies. Dependencies to any java library can be added by the end users in the Java Zeppelin interpreter Dependencies settings section. ### What type of PR is it? * Feature ### Todos * Any feedback from reviewers ### What is the Jira issue? * [ZEPPELIN-3653] ### How should this be tested? Manually * Start the Zeppelin server * Create a new note with the java interpreter binding * Write some java code as per documentation (docs/interpreter/java.md) Unit tests * Run unit tests (JavaInterpreterTest.java and JavaInterpreterUtilsTest.java) ### Screenshots (if appropriate) ### Questions: * Does the licenses files need update? No, the dependency on com.thoughtworks.qdox was already added as part of the Beam Interpreter. * Is there breaking changes for older versions? No. * Does this needs documentation? Yes, it has been added to the PR, see docs/interpreter/java.md. Author: Vincenzo Selvaggio <vselvaggio@hotmail.it> Closes #3092 from selvinsource/java-interpreter and squashes the following commits:c5f96b27d[Vincenzo Selvaggio] Excluding java interpreter from zeppelin-server tests.3f85f1cd3[Vincenzo Selvaggio] Removed redundant java profile as result of rebasing.b68634034[Vincenzo Selvaggio] Updated documentation for Java interpreter to be more explicit on the limitations.ce9401079[Vincenzo Selvaggio] Updated Java Interpreter README and documentation.9e9a859e9[Vincenzo Selvaggio] Stylecheck fixes.706aa0795[Vincenzo Selvaggio] PR reviews changes: -updated interpreter list -direct import of java module and update related README -static logger for Java interpreterd2358f5dc[Vincenzo Selvaggio] Updated documentation for Java interpreter by adding relevant examples.b57f1cfd0[Vincenzo Selvaggio] Added Java Interpreter Utils and tests for them.f542a4f61[Vincenzo Selvaggio] Java Interpreter first version
54 lines
1.9 KiB
Markdown
54 lines
1.9 KiB
Markdown
---
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layout: page
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title: Java interpreter in Apache Zeppelin
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description: Run Java code and any distributed java computation library by importing the dependencies in the interpreter configuration.
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group: interpreter
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---
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<!--
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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{% include JB/setup %}
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# Java interpreter for Apache Zeppelin
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<div id="toc"></div>
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## How to use
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Basically, you can write normal java code. You should write the main method inside a class because the interpreter invoke this main to execute the code. Unlike Zeppelin normal pattern, each paragraph is considered as a separate job, there isn't any relation to any other paragraph. For example, a variable defined in one paragraph cannot be used in another one as each paragraph is a self contained java main class that is executed and the output returned to Zeppelin.
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The following is a demonstration of a word count example with data represented as a java Map and displayed leveraging Zeppelin's built in visualization using the utility method `JavaInterpreterUtils.displayTableFromSimpleMap`.
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```java
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%java
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import java.util.HashMap;
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import java.util.Map;
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import org.apache.zeppelin.java.JavaInterpreterUtils;
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public class HelloWorld {
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public static void main(String[] args) {
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Map<String, Long> counts = new HashMap<>();
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counts.put("hello",4L);
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counts.put("world",5L);
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System.out.println(JavaInterpreterUtils.displayTableFromSimpleMap("Word","Count", counts));
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}
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}
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```
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