[[setup]]
== Set up

MapStruct is a Java annotation processor based on http://www.jcp.org/en/jsr/detail?id=269[JSR 269] and as such can be used within command line builds (javac, Ant, Maven etc.) as well as from within your IDE.

It comprises the following artifacts:

* _org.mapstruct:mapstruct_: contains the required annotations such as `@Mapping`
* _org.mapstruct:mapstruct-processor_: contains the annotation processor which generates mapper implementations

=== Apache Maven

For Maven based projects add the following to your POM file in order to use MapStruct:

.Maven configuration
====
[source, xml, linenums]
[subs="verbatim,attributes"]
----
...
<properties>
    <org.mapstruct.version>{mapstructVersion}</org.mapstruct.version>
</properties>
...
<dependencies>
    <dependency>
        <groupId>org.mapstruct</groupId>
        <artifactId>mapstruct</artifactId>
        <version>${org.mapstruct.version}</version>
    </dependency>
</dependencies>
...
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <annotationProcessorPaths>
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>${org.mapstruct.version}</version>
                    </path>
                </annotationProcessorPaths>
            </configuration>
        </plugin>
    </plugins>
</build>
...
----
====

[TIP]
====
If you are working with the Eclipse IDE, make sure to have a current version of the http://www.eclipse.org/m2e/[M2E plug-in].
When importing a Maven project configured as shown above, it will set up the MapStruct annotation processor so it runs right in the IDE, whenever you save a mapper type.
Neat, isn't it?

To double check that everything is working as expected, go to your project's properties and select "Java Compiler" -> "Annotation Processing" -> "Factory Path".
The MapStruct processor JAR should be listed and enabled there.
Any processor options configured via the compiler plug-in (see below) should be listed under "Java Compiler" -> "Annotation Processing".

If the processor is not kicking in, check that the configuration of annotation processors through M2E is enabled.
To do so, go to "Preferences" -> "Maven" -> "Annotation Processing" and select "Automatically configure JDT APT".
Alternatively, specify the following in the `properties` section of your POM file: `<m2e.apt.activation>jdt_apt</m2e.apt.activation>`.

Also make sure that your project is using Java 1.8 or later (project properties -> "Java Compiler" -> "Compile Compliance Level").
It will not work with older versions.
====

=== Gradle

Add the following to your Gradle build file in order to enable MapStruct:

.Gradle configuration
====
[source, groovy, linenums]
[subs="verbatim,attributes"]
----
...
plugins {
    ...
    id "com.diffplug.eclipse.apt" version "3.26.0" // Only for Eclipse
}

dependencies {
    ...
    implementation "org.mapstruct:mapstruct:${mapstructVersion}"
    annotationProcessor "org.mapstruct:mapstruct-processor:${mapstructVersion}"

    // If you are using mapstruct in test code
    testAnnotationProcessor "org.mapstruct:mapstruct-processor:${mapstructVersion}"
}
...
----
====

You can find a complete example in the https://github.com/mapstruct/mapstruct-examples/tree/master/mapstruct-on-gradle[mapstruct-examples] project on GitHub.


=== Apache Ant

Add the `javac` task configured as follows to your _build.xml_ file in order to enable MapStruct in your Ant-based project. Adjust the paths as required for your project layout.

.Ant configuration
====
[source, xml, linenums]
[subs="verbatim,attributes"]
----
...
<javac
    srcdir="src/main/java"
    destdir="target/classes"
    classpath="path/to/mapstruct-{mapstructVersion}.jar">
    <compilerarg line="-processorpath path/to/mapstruct-processor-{mapstructVersion}.jar"/>
    <compilerarg line="-s target/generated-sources"/>
</javac>
...
----
====

You can find a complete example in the https://github.com/mapstruct/mapstruct-examples/tree/master/mapstruct-on-ant[mapstruct-examples] project on GitHub.

[[configuration-options]]
=== Configuration options

The MapStruct code generator can be configured using _annotation processor options_.

When invoking javac directly, these options are passed to the compiler in the form _-Akey=value_. When using MapStruct via Maven, any processor options can be passed using `compilerArgs` within the configuration of the Maven processor plug-in like this:

.Maven configuration
====
[source, xml, linenums]
[subs="verbatim,attributes"]
----
...
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.5.1</version>
    <configuration>
        <source>1.8</source>
        <target>1.8</target>
        <annotationProcessorPaths>
            <path>
                <groupId>org.mapstruct</groupId>
                <artifactId>mapstruct-processor</artifactId>
                <version>${org.mapstruct.version}</version>
            </path>
        </annotationProcessorPaths>
        <!-- due to problem in maven-compiler-plugin, for verbose mode add showWarnings -->
        <showWarnings>true</showWarnings>
        <compilerArgs>
            <arg>
                -Amapstruct.suppressGeneratorTimestamp=true
            </arg>
            <arg>
                -Amapstruct.suppressGeneratorVersionInfoComment=true
            </arg>
            <arg>
                -Amapstruct.verbose=true
            </arg>
        </compilerArgs>
    </configuration>
</plugin>
...
----
====

.Gradle configuration
====
[source, groovy, linenums]
[subs="verbatim,attributes"]
----
...
compileJava {
    options.compilerArgs += [
        '-Amapstruct.suppressGeneratorTimestamp=true',
        '-Amapstruct.suppressGeneratorVersionInfoComment=true',
        '-Amapstruct.verbose=true'
    ]
}
...
----
====

The following options exist:

.MapStruct processor options
[cols="1,2a,1"]
|===
|Option|Purpose|Default

|`mapstruct.
suppressGeneratorTimestamp`
|If set to `true`, the creation of a time stamp in the `@Generated` annotation in the generated mapper classes is suppressed.
|`false`

|`mapstruct.verbose`
|If set to `true`, MapStruct in which MapStruct logs its major decisions. Note, at the moment of writing in Maven, also `showWarnings` needs to be added due to a problem in the maven-compiler-plugin configuration.
|`false`

|`mapstruct.
suppressGeneratorVersionInfoComment`
|If set to `true`, the creation of the `comment` attribute in the `@Generated` annotation in the generated mapper classes is suppressed. The comment contains information about the version of MapStruct and about the compiler used for the annotation processing.
|`false`

|`mapstruct.defaultComponentModel`
|The name of the component model (see <<retrieving-mapper>>) based on which mappers should be generated.

Supported values are:

* `default`: the mapper uses no component model, instances are typically retrieved via `Mappers#getMapper(Class)`
* `cdi`: the generated mapper is an application-scoped (from javax.enterprise.context or jakarta.enterprise.context, depending on which one is available with javax.inject having priority) CDI bean and can be retrieved via `@Inject`
* `spring`: the generated mapper is a singleton-scoped Spring bean and can be retrieved via `@Autowired`
* `jsr330`: the generated mapper is annotated with {@code @Named} and can be retrieved via `@Inject` (from javax.inject or jakarta.inject, depending which one is available with javax.inject having priority), e.g. using Spring
* `jakarta`: the generated mapper is annotated with {@code @Named} and can be retrieved via `@Inject` (from jakarta.inject), e.g. using Spring
* `jakarta-cdi`: the generated mapper is an application-scoped (from jakarta.enterprise.context) CDI bean and can be retrieved via `@Inject`

If a component model is given for a specific mapper via `@Mapper#componentModel()`, the value from the annotation takes precedence.
|`default`

|`mapstruct.defaultInjectionStrategy`
| The type of the injection in mapper via parameter `uses`. This is only used on annotated based component models
  such as CDI, Spring and JSR 330.

Supported values are:

* `field`: dependencies will be injected in fields
* `constructor`: will be generated constructor. Dependencies will be injected via constructor.

When CDI `componentModel` a default constructor will also be generated.
If a injection strategy is given for a specific mapper via `@Mapper#injectionStrategy()`, the value from the annotation takes precedence over the option.
|`field`

|`mapstruct.unmappedTargetPolicy`
|The default reporting policy to be applied in case an attribute of the target object of a mapping method is not populated with a source value.

Supported values are:

* `ERROR`: any unmapped target property will cause the mapping code generation to fail
* `WARN`: any unmapped target property will cause a warning at build time
* `IGNORE`: unmapped target properties are ignored

If a policy is given for a specific mapper via `@Mapper#unmappedTargetPolicy()`, the value from the annotation takes precedence.
If a policy is given for a specific bean mapping via `@BeanMapping#unmappedTargetPolicy()`, it takes precedence over both `@Mapper#unmappedTargetPolicy()` and the option.
|`WARN`

|`mapstruct.unmappedSourcePolicy`
|The default reporting policy to be applied in case an attribute of the source object of a mapping method is not populated with a target value.

Supported values are:

* `ERROR`: any unmapped source property will cause the mapping code generation to fail
* `WARN`: any unmapped source property will cause a warning at build time
* `IGNORE`: unmapped source properties are ignored

If a policy is given for a specific mapper via `@Mapper#unmappedSourcePolicy()`, the value from the annotation takes precedence.
If a policy is given for a specific bean mapping via `@BeanMapping#ignoreUnmappedSourceProperties()`, it takes precedence over both `@Mapper#unmappedSourcePolicy()` and the option.
|`IGNORE`

|`mapstruct.
disableBuilders`
|If set to `true`, then MapStruct will not use builder patterns when doing the mapping. This is equivalent to doing `@Mapper( builder = @Builder( disableBuilder = true ) )` for all of your mappers.
|`false`

|`mapstruct.nullValueIterableMappingStrategy`
|The strategy to be applied when `null` is passed as a source value to an iterable mapping.

Supported values are:

* `RETURN_NULL`: if `null` is passed as a source value, then `null` will be returned
* `RETURN_DEFAULT`: if `null` is passed then a default value (empty collection) will be returned

If a strategy is given for a specific mapper via `@Mapper#nullValueIterableMappingStrategy()`, the value from the annotation takes precedence.
If a strategy is given for a specific iterable mapping via `@IterableMapping#nullValueMappingStrategy()`, it takes precedence over both `@Mapper#nullValueIterableMappingStrategy()` and the option.
|`RETURN_NULL`

|`mapstruct.nullValueMapMappingStrategy`
|The strategy to be applied when `null` is passed as a source value to a map mapping.

Supported values are:

* `RETURN_NULL`: if `null` is passed as a source value, then `null` will be returned
* `RETURN_DEFAULT`: if `null` is passed then a default value (empty map) will be returned

If a strategy is given for a specific mapper via `@Mapper#nullValueMapMappingStrategy()`, the value from the annotation takes precedence.
If a strategy is given for a specific map mapping via `@MapMapping#nullValueMappingStrategy()`, it takes precedence over both `@Mapper#nullValueMapMappingStrategy()` and the option.
|`RETURN_NULL`
|===

=== Using MapStruct with the Java Module System

MapStruct can be used with Java 9 and higher versions.

To allow usage of the `@Generated` annotation `java.annotation.processing.Generated` (part of the `java.compiler` module) can be enabled.

=== IDE Integration

There are optional MapStruct plugins for IntelliJ and Eclipse that allow you to have additional completion support (and more) in the annotations.

==== IntelliJ

The https://plugins.jetbrains.com/plugin/10036-mapstruct-support[MapStruct IntelliJ] plugin offers assistance in projects that use MapStruct.

Some features include:

* Code completion in `target`, `source`, `expression`
* Go To Declaration for properties in `target` and `source`
* Find Usages of properties in `target` and `source`
* Refactoring support
* Errors and Quick Fixes

==== Eclipse

The https://marketplace.eclipse.org/content/mapstruct-eclipse-plugin[MapStruct Eclipse] Plugin offers assistance in projects that use MapStruct.

Some features include:

* Code completion in `target` and `source`
* Quick Fixes