How to setup a Java web application using Gradle

For basic java and Gradle, it's really simple. All you need is one line in build.gradle file and you can start compiling Java source under src/main/java folder.

apply plugin: 'java'

But to setup a useful web application, you would need little more. Here I have another example of Gradle 2.7 script file for building a Java web application. I also have noted few things I have discovered in the comments.

# A Java web app project

# There should be a src/main/webapp as web content directory
apply plugin: 'war'
apply plugin: 'jetty'

# Change jetty default port from 8080
httpPort = 9000

# A repository must be given to fetch dependencies below.
repositories {
    mavenCentral()
}

# Library dependencies
dependencies {
    // JDK lang support
    // Ouch! Gradle does not support 'provided' scope! Let's use compile for now.
    //provided 'org.projectlombok:lombok:1.16.6'
    compile 'org.projectlombok:lombok:1.16.6'

    // Testing
    testCompile 'junit:junit:4.12',
        'org.hamcrest:hamcrest-library:1.3'

    // Database
    runtime 'mysql:mysql-connector-java:5.1.37'   

    // Scripting
    //runtime 'org.codehaus.groovy:groovy-all:2.4.5'
    /*
    NOTE: Error if you include groovy with gradle+jetty!!!
            java.lang.ExceptionInInitializerError:
        groovy.lang.GroovyRuntimeException: Conflicting module versions. Module [groovy-all is loaded in version 2.3.10 and you are trying to load version 2.4.5
             // Verify your groovy version using the following:
        import javax.script.*
        out.println(new ScriptEngineManager().getEngineFactories())
        out.println(org.codehaus.groovy.jsr223.GroovyScriptEngineFactory.class.getProtectionDomain().getCodeSource().getLocation())
    */ 
}

I also have this JSP in src/main/webapp/script.jsp folder

<%@ page import="javax.script.*, java.io.*" %>

<%
// Initialize parameters
String engineName = request.getParameter("engine");
if (engineName == null) engineName = "Groovy";
String code = request.getParameter("code");
if (code == null) code = "";
%>

<!-- form: Script input code -->
<h1>Scripting</h1>
<form method="POST">
<textarea name="code" cols="120" rows="25"><%= code %></textarea>
<p/><input type="submit" value="Submit"/>
</form>

<pre>
<%
if (request.getMethod().equals("POST")) {
    // Process form and evaluate script code
    ScriptEngine se = new ScriptEngineManager().getEngineByName(engineName);
    if (se == null) {
        out.println("ERROR: " + engineName + " engine not found! Use 'engine' parameter to change it.");
    } else {
        try {
            Bindings b = se.createBindings();
            b.put("request", request);
            b.put("out", out);
            Object result = se.eval(code, b);
            
            out.println(engineName + " script result:");
            out.println("" + result);
        } catch (Exception e) {
            out.println("ERROR: " + engineName + " script failed to evaluate!");
            e.printStackTrace(new PrintWriter(out));
        }
    }
}
%>

</pre>

With this script.jsp, you can write something like this to test out your db connection.

// Groovy script:
import java.sql*
conn = DriverManager.getConnection('jdbc:mysql://localhost/test', 'dev', 'dev123')
out.println("conn=" + conn)
conn.close()

And just for fun, I have created a data class using ProjectLombok generator in src/main/java/myjava/MyData.java

package myjava;
import java.util.*;

@lombok.Data
public class MyData {
private Integer id;
private String name;
private Date createdDate;
private List<MyData> dataList;
private Map<String, MyData> dataMap;

}

I also have a unit test in src/test/java/myjava/MyDataTest.java

package myjava;

import org.junit.Test;
import static org.junit.Assert.assertThat;
import static org.hamcrest.Matchers.*;

public class MyDataTest {
@Test
public void tesGeneratedGetterSettersAndToString() {
MyData d = new MyData();
d.setId(12345);
d.setName("foo");
assertThat(d.getId(), is(12345));
assertThat(d.getName(), is("foo"));
assertThat(d.toString(), is("MyData(id=12345, name=foo, createdDate=null, dataList=null, dataMap=null)"));
}

}

To compile code, type command: gradle compileJava

To run test, type command: gradle test(A nice feature of Gradle is that it auto generate test reports! Look for them in your build/reports folder.)

To run web app, type command: gradle jettyRun