Readme.md additions

Author: rumpfc

README.md

@@ -1,3 +1,58 @@
 # Protocol Buffer Annotation
 
-Inspired by jackson's fasterxml, a simple library to (de)serialize Protocol Buffer data.
+Inspired by jackson's fasterxml, a simple library to (de)serialize Protocol Buffer data using annotations.
+The usage of Google's protobuf compiler is not necessary.
+
+## Usage
+
+Create an instance of PbObjectMapper and call read/write to read from data/stream or write into one.
+
+```java
+public class SampleClass1 {
+
+    @PbField(field = 1, type = PbFieldType.INT32)
+    private int id;
+
+    @PbField(field = 2, type = PbFieldType.STRING)
+    private String name;
+
+    // Optional Constructor, getter and setter
+}
+```
+
+### Read from Data (byte array)
+
+```java
+try {
+    PbObjectMapper mapper = new ObjectMapper();
+    byte[] sampleData = new byte[]{ 
+        0x08, 0x14,                                     // ID = 20
+        0x12, 0x06, 0x72, 0x75, 0x6D, 0x70, 0x66, 0x63  // name = rumpfc
+    };
+        
+    SampleClass1 sample = mapper.read(sampleData, SampleClass1.class);
+    System.out.println(sample);
+    // SampleClass1{id=20, name='rumpfc'}
+} catch(IOException ex) {
+    ex.printStackTrace();
+}
+```
+
+### Write data (byte array)
+
+```java
+try {
+    PbObjectMapper mapper = new ObjectMapper();
+    
+    SampleClass1 sample = new SampleClass1();
+    sample.setId(20);
+    sample.setName("rumpfc");
+    System.out.println(sample);
+    // SampleClass1{id=20, name='rumpfc'}
+        
+    byte[] output = mapper.write(sample);
+    // hex output = [08 14 12 06 72 75 6D 70 66 63]
+} catch(IOException ex) {
+    ex.printStackTrace();
+}
+```

src/test/java/com/rumpf/mapper/PbObjectMapperTest.java

@@ -47,6 +47,14 @@ public void setId(int id) {
         public void setName(String name) {
             this.name = name;
         }
+
+        @Override
+        public String toString() {
+            return "SampleClass1{" +
+                    "id=" + id +
+                    ", name='" + name + '\'' +
+                    '}';
+        }
     }
 
     private PbObjectMapper mapper;
@@ -58,8 +66,8 @@ public void setup() {
 
     @Test
     public void objectMapperWriteTest() throws Exception {
-        SampleClass1 sample = new SampleClass1(20, "Rumpfi");
-        byte[] expected = new byte[]{ 0x08, 0x14, 0x12, 0x06, 0x52, 0x75, 0x6D, 0x70, 0x66, 0x69};
+        SampleClass1 sample = new SampleClass1(20, "rumpfc");
+        byte[] expected = new byte[]{ 0x08, 0x14, 0x12, 0x06, 0x72, 0x75, 0x6D, 0x70, 0x66, 0x63};
 
         byte[] result = mapper.write(sample);
 
@@ -68,13 +76,15 @@ public void objectMapperWriteTest() throws Exception {
 
     @Test
     public void objectMapperReadTest() throws Exception {
-        byte[] sampleData = new byte[]{ 0x08, 0x14, 0x12, 0x06, 0x52, 0x75, 0x6D, 0x70, 0x66, 0x69};
+        byte[] sampleData = new byte[]{ 0x08, 0x14, 0x12, 0x06, 0x72, 0x75, 0x6D, 0x70, 0x66, 0x63};
 
         SampleClass1 sampleObject = mapper.read(sampleData, SampleClass1.class);
 
+        System.out.println(sampleObject);
+
         Assertions.assertAll(
                 () -> Assertions.assertEquals(20, sampleObject.getId()),
-                () -> Assertions.assertEquals("Rumpfi", sampleObject.getName())
+                () -> Assertions.assertEquals("rumpfc", sampleObject.getName())
         );
     }