Precompile JSP's with Gradle

Question

im trying to change our build process from Maven to Gradle (V 2.9). In Maven i was using precompiling for JSP's like this:

        <plugin>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-jspc-maven-plugin</artifactId>
            <version>9.2.7.v20150116</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <id>jspc</id>
                    <goals>
                        <goal>jspc</goal>
                    </goals>
                    <configuration>
                        <excludes>**\/*inc_page_bottom.jsp,**\/*inc_page_top.jsp</excludes>
                        <includes>**\/*.jsp</includes>
                    </configuration>
                </execution>
            </executions>
        </plugin>

and it was working fine. Now im trying to find a way to do the same with gradle. I've found some informations/build.gradle examples but nothing was working really. Im currently using Tomcat 7 as servlet container and im planning to switch in some weeks to 8. Would be perfect of course to compile them for the target servlet container but first of all i would be happy to precompile them at all like i was doing this with maven for/with jetty.

A part of my current build.gradle which gives me a error:

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.bmuschko:gradle-tomcat-plugin:2.2.4'
    }
}

apply plugin: 'com.bmuschko.tomcat'

tomcat {
    jasper {
        validateXml = true
        errorOnUseBeanInvalidClassAttribute = false
        compilerSourceVM = "1.8"
        compilerTargetVM = "1.8"
    }
}

task compileJsps(type: JavaCompile, dependsOn: 'clean') {
    dependsOn tomcatJasper
    group = 'build'
    description = 'Translates and compiles JSPs'
    classpath = configurations.tomcat + sourceSets.main.output + sourceSets.main.runtimeClasspath
    sourceCompatibility = "1.8"
    targetCompatibility = "1.8"
    destinationDir = file("$buildDir/jasper-classes")
    sourceSets {
        main {
            java {
                srcDir "$buildDir/jasper"
            }
        }
    }
}

dependencies {
    def tomcatVersion = '7.0.59'
    tomcat "org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}",
       "org.apache.tomcat.embed:tomcat-embed-logging-juli:${tomcatVersion}",
       "org.apache.tomcat.embed:tomcat-embed-jasper:${tomcatVersion}"
}

Im getting the following error:

:tomcatJasper FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':tomcatJasper'.
> org.apache.jasper.JasperException: file:/xxx/xxx/xxx/xxx/src/main/webapp/index.jsp (line: 6, column: 0) The value for the useBean class attribute xxx.xxx.xxx.XxxXxx is invalid.

Running this jsp's in Tomcat 7 works fine... Does anybody have a up to date howto or a hint?

Answer 1

With gradle, you can call the JSPC compiler directly. That way it's explicit as to what is going on. We're using something like the following.

A couple of things to note.

1. The JSPC compiler has a dependency on Ant, so that needs to be added to the classpath
2. The JSPC compiler uses log4j, so we create a properties file to output some basic logging
3. The JSPC compiler is embedded within Jetty, which is a "providedCompile" dependency, hence on our runtime classpath.

Anyway, our gradle looks similar to;

configurations {
    jspc
}

dependencies {
    jspc 'org.apache.tomcat:tomcat-jasper:9.0.17'
    jspc 'org.apache.ant:ant:1.10.1'

}

def jspSrc = "$projectDir/src/main/webapp"
def jspJavaSrc = "$buildDir/jsp-java-source"
def jspPackage = "com.example.jsp"

task writeJspcProperties(type: WriteProperties) {
    outputFile = "$buildDir/log4j.jspc.properties"
    property('log4j.rootLogger', 'WARN, stdout')
    property('log4j.logger.org.apache', 'INFO, stdout')
    property('log4j.appender.stdout', 'org.apache.log4j.ConsoleAppender')
    property('log4j.appender.stdout.Target', 'System.out')
    property('log4j.appender.stdout.layout', 'org.apache.log4j.PatternLayout')
    property('log4j.appender.stdout.layout.ConversionPattern', '%d [%C] %m%n')
}

task jspToJava(type: JavaExec, dependsOn: [compileJava, writeJspcProperties]) {

    inputs.dir jspSrc
    outputs.dir jspJavaSrc

    File xmlPartial = file("$jspJavaSrc/WEB-INF/web.xml.partial")

    doFirst {
        // Create the target WEB-INF folder so the JspC can create the web.xml.partial
        File webInfFolder = xmlPartial.getParentFile()
        if (!webInfFolder.exists()) {
            webInfFolder.mkdirs()
        }
    }

    classpath = configurations.jspc + sourceSets.main.runtimeClasspath
    main = 'org.apache.jasper.JspC'
    jvmArgs "-Dlog4j.configuration=file:$buildDir/log4j.jspc.properties"

    args '-webapp', jspSrc,
            '-d', jspJavaSrc,
            '-p', jspPackage,
            '-webxmlencoding', 'UTF-8',
            '-webinc', xmlPartial.absolutePath

    doLast {
        // Merge the partial XML with the original
        String originalXML = file("$jspSrc/WEB-INF/web.xml").text
        String xmlToMerge = xmlPartial.text
        String mergedXML = originalXML.replaceFirst('(?s)(<web-app.*?>)', '$1' + xmlToMerge)
        file("$jspJavaSrc/WEB-INF/web.xml").text = mergedXML
    }
}

[Edit; greatly simplified the JSP compilation]

[Edit 2; explicitly add the tomcat-jasper dependency]

Answer 2

In your main build.gradle at the bottom do

apply from: 'jspc.gradle'

Then your jspc.gradle file looks like:

buildscript {  
    repositories {  
       jcenter()  
    }  


    dependencies {  
        classpath 'com.bmuschko:gradle-tomcat-plugin:2.2.5'  
    }  
}  

apply plugin: com.bmuschko.gradle.tomcat.TomcatPlugin 
apply plugin: 'java'

dependencies {
   def tomcatVersion = '8.0.42'  
    tomcat "org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}",  
           "org.apache.tomcat.embed:tomcat-embed-logging-juli:${tomcatVersion}",  
           "org.apache.tomcat.embed:tomcat-embed-jasper:${tomcatVersion}",  
           "javax.servlet:jstl:1.2"  

    providedCompile "javax.servlet:servlet-api:2.5"  

}

then to use the precompile do:

gradle tomcatJasper