diff --git a/java/bootclasspath.go b/java/bootclasspath.go
new file mode 100644
index 0000000..b140a30
--- /dev/null
+++ b/java/bootclasspath.go
@@ -0,0 +1,145 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package java
+
+import (
+	"fmt"
+
+	"android/soong/android"
+	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
+)
+
+// Contains code that is common to both platform_bootclasspath and bootclasspath_fragment.
+
+// addDependencyOntoApexVariants adds dependencies onto the appropriate apex specific variants of
+// the module as specified in the ApexVariantReference list.
+func addDependencyOntoApexVariants(ctx android.BottomUpMutatorContext, propertyName string, refs []ApexVariantReference, tag blueprint.DependencyTag) {
+	for i, ref := range refs {
+		apex := proptools.StringDefault(ref.Apex, "platform")
+
+		if ref.Module == nil {
+			ctx.PropertyErrorf(propertyName, "missing module name at position %d", i)
+			continue
+		}
+		name := proptools.String(ref.Module)
+
+		addDependencyOntoApexModulePair(ctx, apex, name, tag)
+	}
+}
+
+// addDependencyOntoApexModulePair adds a dependency onto the specified APEX specific variant or the
+// specified module.
+//
+// If apex="platform" then this adds a dependency onto the platform variant of the module. This adds
+// dependencies onto the prebuilt and source modules with the specified name, depending on which
+// ones are available. Visiting must use isActiveModule to select the preferred module when both
+// source and prebuilt modules are available.
+func addDependencyOntoApexModulePair(ctx android.BottomUpMutatorContext, apex string, name string, tag blueprint.DependencyTag) {
+	var variations []blueprint.Variation
+	if apex != "platform" {
+		// Pick the correct apex variant.
+		variations = []blueprint.Variation{
+			{Mutator: "apex", Variation: apex},
+		}
+	}
+
+	addedDep := false
+	if ctx.OtherModuleDependencyVariantExists(variations, name) {
+		ctx.AddFarVariationDependencies(variations, tag, name)
+		addedDep = true
+	}
+
+	// Add a dependency on the prebuilt module if it exists.
+	prebuiltName := android.PrebuiltNameFromSource(name)
+	if ctx.OtherModuleDependencyVariantExists(variations, prebuiltName) {
+		ctx.AddVariationDependencies(variations, tag, prebuiltName)
+		addedDep = true
+	}
+
+	// If no appropriate variant existing for this, so no dependency could be added, then it is an
+	// error, unless missing dependencies are allowed. The simplest way to handle that is to add a
+	// dependency that will not be satisfied and the default behavior will handle it.
+	if !addedDep {
+		// Add dependency on the unprefixed (i.e. source or renamed prebuilt) module which we know does
+		// not exist. The resulting error message will contain useful information about the available
+		// variants.
+		reportMissingVariationDependency(ctx, variations, name)
+
+		// Add dependency on the missing prefixed prebuilt variant too if a module with that name exists
+		// so that information about its available variants will be reported too.
+		if ctx.OtherModuleExists(prebuiltName) {
+			reportMissingVariationDependency(ctx, variations, prebuiltName)
+		}
+	}
+}
+
+// reportMissingVariationDependency intentionally adds a dependency on a missing variation in order
+// to generate an appropriate error message with information about the available variations.
+func reportMissingVariationDependency(ctx android.BottomUpMutatorContext, variations []blueprint.Variation, name string) {
+	modules := ctx.AddFarVariationDependencies(variations, nil, name)
+	if len(modules) != 1 {
+		panic(fmt.Errorf("Internal Error: expected one module, found %d", len(modules)))
+		return
+	}
+	if modules[0] != nil {
+		panic(fmt.Errorf("Internal Error: expected module to be missing but was found: %q", modules[0]))
+		return
+	}
+}
+
+// ApexVariantReference specifies a particular apex variant of a module.
+type ApexVariantReference struct {
+	// The name of the module apex variant, i.e. the apex containing the module variant.
+	//
+	// If this is not specified then it defaults to "platform" which will cause a dependency to be
+	// added to the module's platform variant.
+	Apex *string
+
+	// The name of the module.
+	Module *string
+}
+
+// BootclasspathFragmentsDepsProperties contains properties related to dependencies onto fragments.
+type BootclasspathFragmentsDepsProperties struct {
+	// The names of the bootclasspath_fragment modules that form part of this module.
+	Fragments []ApexVariantReference
+}
+
+// addDependenciesOntoFragments adds dependencies to the fragments specified in this properties
+// structure.
+func (p *BootclasspathFragmentsDepsProperties) addDependenciesOntoFragments(ctx android.BottomUpMutatorContext) {
+	addDependencyOntoApexVariants(ctx, "fragments", p.Fragments, bootclasspathFragmentDepTag)
+}
+
+// bootclasspathDependencyTag defines dependencies from/to bootclasspath_fragment,
+// prebuilt_bootclasspath_fragment and platform_bootclasspath onto either source or prebuilt
+// modules.
+type bootclasspathDependencyTag struct {
+	blueprint.BaseDependencyTag
+
+	name string
+}
+
+func (t bootclasspathDependencyTag) ExcludeFromVisibilityEnforcement() {
+}
+
+// Dependencies that use the bootclasspathDependencyTag instances are only added after all the
+// visibility checking has been done so this has no functional effect. However, it does make it
+// clear that visibility is not being enforced on these tags.
+var _ android.ExcludeFromVisibilityEnforcementTag = bootclasspathDependencyTag{}
+
+// The tag used for dependencies onto bootclasspath_fragments.
+var bootclasspathFragmentDepTag = bootclasspathDependencyTag{name: "fragment"}