minor jaackson example and new streaming logic for large files

Author: eugenp

core-java/src/test/java/org/baeldung/java/CoreJavaIoIntegrationTest.java

@@ -6,6 +6,7 @@
 import java.util.Scanner;
 
 import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.LineIterator;
 import org.junit.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -29,9 +30,9 @@ public final void givenUsingGuava_whenIteratingAFile_thenCorrect() throws IOExce
     }
 
     @Test
-    public final void givenUsingCommonsIo_whenIteratingAFile_thenCorrect() throws IOException {
-        final String path = "G:\\full\\train\\input\\" + "trainDataNegative.csv";
-        // final String path = "G:\\full\\train\\input\\" + "trainDataPositive.csv";
+    public final void givenUsingCommonsIo_whenIteratingAFileInMemory_thenCorrect() throws IOException {
+        // final String path = "G:\\full\\train\\input\\" + "trainDataNegative.csv";
+        final String path = "G:\\full\\train\\input\\" + "trainDataPositive.csv";
 
         logMemory();
         FileUtils.readLines(new File(path));
@@ -70,6 +71,26 @@ public final void whenStreamingThroughAFile_thenCorrect() throws IOException {
         logMemory();
     }
 
+    @Test
+    public final void givenUsingApacheIo_whenStreamingThroughAFile_thenCorrect() throws IOException {
+        final String path = "G:\\full\\train\\input\\" + "trainDataNegative.csv";
+        // final String path = "G:\\full\\train\\input\\" + "trainDataPositive.csv";
+
+        logMemory();
+
+        final LineIterator it = FileUtils.lineIterator(new File(path), "UTF-8");
+        try {
+            while (it.hasNext()) {
+                final String line = it.nextLine();
+                // do something with line
+            }
+        } finally {
+            LineIterator.closeQuietly(it);
+        }
+
+        logMemory();
+    }
+
     // utils
 
     private final void logMemory() {

jackson/src/test/java/org/baeldung/jackson/try1/IEntity.java

@@ -0,0 +1,4 @@
+package org.baeldung.jackson.try1;
+public interface IEntity {
+    public int getId();
+}

jackson/src/test/java/org/baeldung/jackson/try1/JacksonDeserializationUnitTest.java

@@ -0,0 +1,25 @@
+package org.baeldung.jackson.try1;
+
+import static org.hamcrest.Matchers.notNullValue;
+import static org.junit.Assert.assertThat;
+
+import java.io.IOException;
+
+import org.baeldung.jackson.dtos.ItemWithSerializer;
+import org.junit.Test;
+
+import com.fasterxml.jackson.core.JsonParseException;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class JacksonDeserializationUnitTest {
+
+    @Test
+    public final void givenDeserializerIsOnClass_whenDeserializingCustomRepresentation_thenCorrect() throws JsonParseException, JsonMappingException, IOException {
+        final String json = "{\"id\":1,\"itemName\":\"theItem\",\"owner\":2}";
+
+        final ItemWithSerializer readValue = new ObjectMapper().readValue(json, ItemWithSerializer.class);
+        assertThat(readValue, notNullValue());
+    }
+
+}

jackson/src/test/java/org/baeldung/jackson/try1/RestLoaderRequest.java

@@ -0,0 +1,38 @@
+package org.baeldung.jackson.try1;
+
+import java.io.Serializable;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+
+@JsonDeserialize(using = RestLoaderRequestDeserializer.class)
+// @Produces(MediaType.APPLICATION_JSON)
+public class RestLoaderRequest<T extends IEntity> implements Serializable {
+    private T entity; // entity to load field to
+    private String className; // actual class of entity
+    private String fieldName; // fieldName to lazy REST load
+
+    public String getFieldName() {
+        return fieldName;
+    }
+
+    public void setFieldName(final String fieldName) {
+        this.fieldName = fieldName;
+    }
+
+    public String getClassName() {
+        return className;
+    }
+
+    public void setClassName(final String className) {
+        this.className = className;
+    }
+
+    public T getEntity() {
+        return entity;
+    }
+
+    public void setEntity(final T entity) {
+        this.entity = entity;
+    }
+
+}

jackson/src/test/java/org/baeldung/jackson/try1/RestLoaderRequestDeserializer.java

@@ -0,0 +1,37 @@
+package org.baeldung.jackson.try1;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonNode;
+
+public class RestLoaderRequestDeserializer extends JsonDeserializer<RestLoaderRequest<IEntity>> {
+
+    @Override
+    public RestLoaderRequest<IEntity> deserialize(final JsonParser jp, final DeserializationContext ctxt) throws IOException, JsonProcessingException {
+        try {
+            final ObjectCodec objectCodec = jp.getCodec();
+            final JsonNode node = objectCodec.readTree(jp);
+            final String className = node.get("className").textValue();
+            final String fieldName = node.get("fieldName").textValue();
+
+            final Class<?> clazz = Class.forName(className);
+
+            final JsonNode rawEntityNode = node.get("entity");
+            // How to deserialize rawEntityNode to T based on className ?
+
+            final RestLoaderRequest<IEntity> request = new RestLoaderRequest<IEntity>();
+            request.setClassName(className);
+            request.setFieldName(fieldName);
+        } catch (final ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+}