feat: Built-in FormTypeMapper and TextTypeMapper

Author: thced

src/main/java/com/retailsvc/http/internal/FormTypeMapper.java

@@ -0,0 +1,24 @@
+package com.retailsvc.http.internal;
+
+import com.retailsvc.http.TypeMapper;
+
+/**
+ * Built-in {@link TypeMapper} for {@code application/x-www-form-urlencoded}. Reads delegate to
+ * {@link FormUrlEncodedParser}. Writes are not supported — form-encoded responses are unusual and
+ * intentionally left out until a real need surfaces.
+ */
+public final class FormTypeMapper implements TypeMapper {
+
+  private final FormUrlEncodedParser parser = new FormUrlEncodedParser();
+
+  @Override
+  public Object readFrom(byte[] body, String contentTypeHeader) {
+    return parser.parse(body, contentTypeHeader);
+  }
+
+  @Override
+  public byte[] writeTo(Object value) {
+    throw new UnsupportedOperationException(
+        "application/x-www-form-urlencoded write is not supported; register a custom TypeMapper");
+  }
+}

src/main/java/com/retailsvc/http/internal/TextTypeMapper.java

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+package com.retailsvc.http.internal;
+
+import com.retailsvc.http.TypeMapper;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Built-in {@link TypeMapper} for {@code text/plain}. Reads decode bytes using the charset declared
+ * on {@code Content-Type} (default UTF-8). Writes return {@code String.valueOf(value)} encoded as
+ * UTF-8.
+ */
+public final class TextTypeMapper implements TypeMapper {
+
+  private final TextPlainParser parser = new TextPlainParser();
+
+  @Override
+  public Object readFrom(byte[] body, String contentTypeHeader) {
+    return parser.parse(body, contentTypeHeader);
+  }
+
+  @Override
+  public byte[] writeTo(Object value) {
+    return String.valueOf(value).getBytes(StandardCharsets.UTF_8);
+  }
+}

src/test/java/com/retailsvc/http/internal/FormTypeMapperTest.java

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+package com.retailsvc.http.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class FormTypeMapperTest {
+
+  private final FormTypeMapper mapper = new FormTypeMapper();
+
+  @Test
+  void readsKeyValuePairs() {
+    byte[] body = "name=Alice&color=blue".getBytes(StandardCharsets.UTF_8);
+    Object parsed = mapper.readFrom(body, "application/x-www-form-urlencoded");
+    assertThat(parsed).isInstanceOf(Map.class);
+    @SuppressWarnings("unchecked")
+    Map<String, Object> m = (Map<String, Object>) parsed;
+    assertThat(m).containsEntry("name", "Alice").containsEntry("color", "blue");
+  }
+
+  @Test
+  void writeToIsUnsupported() {
+    assertThatThrownBy(() -> mapper.writeTo(Map.of("k", "v")))
+        .isInstanceOf(UnsupportedOperationException.class);
+  }
+}

src/test/java/com/retailsvc/http/internal/TextTypeMapperTest.java

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+package com.retailsvc.http.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.nio.charset.StandardCharsets;
+import org.junit.jupiter.api.Test;
+
+class TextTypeMapperTest {
+
+  private final TextTypeMapper mapper = new TextTypeMapper();
+
+  @Test
+  void readsUtf8ByDefault() {
+    byte[] body = "hello".getBytes(StandardCharsets.UTF_8);
+    assertThat(mapper.readFrom(body, "text/plain")).isEqualTo("hello");
+  }
+
+  @Test
+  void readsExplicitCharset() {
+    byte[] body = "räksmörgås".getBytes(StandardCharsets.ISO_8859_1);
+    assertThat(mapper.readFrom(body, "text/plain; charset=ISO-8859-1")).isEqualTo("räksmörgås");
+  }
+
+  @Test
+  void writesStringValueAsUtf8() {
+    assertThat(mapper.writeTo("ok")).isEqualTo("ok".getBytes(StandardCharsets.UTF_8));
+    assertThat(mapper.writeTo(42)).isEqualTo("42".getBytes(StandardCharsets.UTF_8));
+    assertThat(mapper.writeTo(null)).isEqualTo("null".getBytes(StandardCharsets.UTF_8));
+  }
+}