Add java/lang/Class::forName

Author: dlunch

java_runtime/src/classes/java/lang/class.rs

@@ -1,6 +1,7 @@
 use alloc::vec;
 
 use java_class_proto::{JavaFieldProto, JavaMethodProto};
+use java_constants::MethodAccessFlags;
 use jvm::{
     ClassInstanceRef, Jvm, Result,
     runtime::{JavaLangClass, JavaLangClassLoader, JavaLangString},
@@ -33,6 +34,12 @@ impl Class {
                     Self::get_resource_as_stream,
                     Default::default(),
                 ),
+                JavaMethodProto::new(
+                    "forName",
+                    "(Ljava/lang/String;)Ljava/lang/Class;",
+                    Self::for_name,
+                    MethodAccessFlags::STATIC,
+                ),
             ],
             fields: vec![
                 JavaFieldProto::new("raw", "[B", Default::default()), // raw rust pointer of Box<dyn Class>
@@ -87,4 +94,14 @@ impl Class {
         jvm.invoke_virtual(&class_loader, "getResourceAsStream", "(Ljava/lang/String;)Ljava/io/InputStream;", (name,))
             .await
     }
+
+    async fn for_name(jvm: &Jvm, _context: &mut RuntimeContext, name: ClassInstanceRef<String>) -> Result<ClassInstanceRef<Class>> {
+        tracing::debug!("java.lang.Class::forName({:?})", &name);
+
+        let rust_name = JavaLangString::to_rust_string(jvm, &name).await?;
+        let qualified_name = rust_name.replace('.', "/");
+        let class = jvm.get_class(&qualified_name).unwrap().java_class();
+
+        Ok(class.into())
+    }
 }

java_runtime/tests/classes/java/lang/test_class.rs

@@ -1,4 +1,8 @@
-use jvm::{Result, runtime::JavaLangClass};
+use java_runtime::classes::java::lang::Class;
+use jvm::{
+    ClassInstanceRef, Result,
+    runtime::{JavaLangClass, JavaLangString},
+};
 
 use test_utils::test_jvm;
 
@@ -39,3 +43,18 @@ async fn test_is_assignable_from() -> Result<()> {
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_for_name() -> Result<()> {
+    let jvm = test_jvm().await?;
+
+    let class_name = JavaLangString::from_rust_string(&jvm, "java.lang.String").await?;
+    let class: ClassInstanceRef<Class> = jvm
+        .invoke_static("java/lang/Class", "forName", "(Ljava/lang/String;)Ljava/lang/Class;", (class_name,))
+        .await?;
+
+    let rust_class = JavaLangClass::to_rust_class(&jvm, &class).await?;
+    assert_eq!(rust_class.name(), "java/lang/String");
+
+    Ok(())
+}