BAEL-6310 - guide to JacksonJr

jackson-jr/pom.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>jackson-jr</artifactId>
+    <name>jackson-jr</name>
+    <packaging>pom</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <!--jackson jr all -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.jr</groupId>
+            <artifactId>jackson-jr-all</artifactId>
+            <version>2.15.2</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.jr</groupId>
+            <artifactId>jackson-jr-annotation-support</artifactId>
+            <version>2.15.2</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>RELEASE</version>
+            <scope>compile</scope>
+        </dependency>
+
+    </dependencies>
+
+</project>

jackson-jr/src/main/java/com/baeldung/jacksonjr/CustomDateDeserializer.java

@@ -0,0 +1,22 @@
+package com.baeldung.jacksonjr;
+
+import com.fasterxml.jackson.jr.ob.api.ValueReader;
+import com.fasterxml.jackson.jr.ob.impl.JSONReader;
+import com.fasterxml.jackson.jr.private_.JsonParser;
+
+import java.io.IOException;
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+
+public class CustomDateDeserializer extends ValueReader {
+    private final static DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
+
+    public CustomDateDeserializer () {
+        super(LocalDate.class);
+    }
+
+    @Override
+    public Object read (JSONReader jsonReader, JsonParser jsonParser) throws IOException {
+        return LocalDate.parse(jsonParser.getText(), dtf);
+    }
+}

jackson-jr/src/main/java/com/baeldung/jacksonjr/CustomDateSerializer.java

@@ -0,0 +1,20 @@
+package com.baeldung.jacksonjr;
+
+import com.fasterxml.jackson.jr.ob.api.ValueWriter;
+import com.fasterxml.jackson.jr.ob.impl.JSONWriter;
+import com.fasterxml.jackson.jr.private_.JsonGenerator;
+
+import java.io.IOException;
+import java.time.LocalDate;
+
+public class CustomDateSerializer implements ValueWriter {
+    @Override
+    public void writeValue (JSONWriter jsonWriter, JsonGenerator jsonGenerator, Object o) throws IOException {
+        jsonGenerator.writeString(o.toString());
+    }
+
+    @Override
+    public Class<?> valueType () {
+        return LocalDate.class;
+    }
+}

jackson-jr/src/main/java/com/baeldung/jacksonjr/JacksonJrFeatures.java

@@ -0,0 +1,96 @@
+package com.baeldung.jacksonjr;
+
+import com.fasterxml.jackson.jr.annotationsupport.JacksonAnnotationExtension;
+import com.fasterxml.jackson.jr.ob.JSON;
+import com.fasterxml.jackson.jr.ob.JacksonJrExtension;
+import com.fasterxml.jackson.jr.ob.api.ExtensionContext;
+
+import java.io.IOException;
+import java.util.LinkedHashMap;
+
+public class JacksonJrFeatures {
+
+    public static String jsonObject() throws IOException {
+        return JSON.std
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .asString(new LinkedHashMap<String, Object>() {{
+                    put("name", "John Doe");
+                    put("age", 30);
+                }});
+    }
+
+    public static String jsonComposer() throws IOException {
+        return JSON.std
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .composeString()
+                .startObject()
+                    .startArrayField("objectArray")
+                        .startObject()
+                            .put("name", "name1")
+                            .put("age", 11)
+                        .end()
+                        .startObject()
+                            .put("name", "name2")
+                            .put("age", 12)
+                        .end()
+                    .end()
+                    .startArrayField("array")
+                        .add(1)
+                        .add(2)
+                        .add(3)
+                    .end()
+                    .startObjectField("object")
+                        .put("name", "name3")
+                        .put("age", 13)
+                    .end()
+                    .put("last", true)
+                .end()
+                .finish();
+    }
+
+    public static String objectSerialization(Person person) throws IOException {
+        return JSON.std
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .asString(person);
+    }
+
+    public static String objectAnnotationSerialization(Person person) throws IOException {
+        return JSON.builder()
+                .register(JacksonAnnotationExtension.std)
+                .build()
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .asString(person);
+    }
+
+    public static String customObjectSerialization(Person person) throws IOException {
+        return JSON.builder()
+                .register(new JacksonJrExtension() {
+                    @Override
+                    protected void register (ExtensionContext extensionContext) {
+                        extensionContext.insertProvider(new MyHandlerProvider());
+                    }
+                })
+                .build()
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .asString(person);
+    }
+
+    public static Person objectDeserialization(String json) throws IOException {
+        return JSON.std
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .beanFrom(Person.class, json);
+    }
+
+    public static Person customObjectDeserialization(String json) throws IOException {
+        return JSON.builder()
+                .register(new JacksonJrExtension() {
+                    @Override
+                    protected void register (ExtensionContext extensionContext) {
+                        extensionContext.insertProvider(new MyHandlerProvider());
+                    }
+                })
+                .build()
+                .with(JSON.Feature.PRETTY_PRINT_OUTPUT)
+                .beanFrom(Person.class, json);
+    }
+}

jackson-jr/src/main/java/com/baeldung/jacksonjr/MyHandlerProvider.java

@@ -0,0 +1,28 @@
+package com.baeldung.jacksonjr;
+
+import com.fasterxml.jackson.jr.ob.api.ReaderWriterProvider;
+import com.fasterxml.jackson.jr.ob.api.ValueReader;
+import com.fasterxml.jackson.jr.ob.api.ValueWriter;
+import com.fasterxml.jackson.jr.ob.impl.JSONReader;
+import com.fasterxml.jackson.jr.ob.impl.JSONWriter;
+
+import java.time.LocalDate;
+
+public class MyHandlerProvider extends ReaderWriterProvider {
+
+    public ValueWriter findValueWriter (JSONWriter writeContext,
+                                        Class<?> type) {
+        if (type == LocalDate.class) {
+            return new CustomDateSerializer();
+        }
+        return null;
+    }
+
+    @Override
+    public ValueReader findValueReader (JSONReader readContext, Class<?> type) {
+        if (type.equals(LocalDate.class)) {
+            return new CustomDateDeserializer();
+        }
+        return null;
+    }
+}

jackson-jr/src/main/java/com/baeldung/jacksonjr/Person.java

@@ -0,0 +1,19 @@
+package com.baeldung.jacksonjr;
+
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDate;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class Person {
+    @JsonProperty("person_name")
+    private String name;
+    private int age;
+    private LocalDate birthDate;
+}

jackson-jr/src/test/java/com/baeldung/jacksonjr/JacksonJrFeaturesUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.jacksonjr;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.time.LocalDate;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class JacksonJrFeaturesUnitTest {
+
+    @Test
+    public void whenSerializingObject_thenReturnJson() throws IOException {
+        String json = JacksonJrFeatures.jsonObject();
+        assertTrue(json.contains("name"));
+        assertTrue(json.contains("age"));
+    }
+
+    @Test
+    public void whenSerializingComposer_thenReturnJson() throws IOException {
+        String json = JacksonJrFeatures.jsonComposer();
+        assertTrue(json.contains("objectArray"));
+        assertTrue(json.contains("object"));
+    }
+
+    @Test
+    public void whenSerializingSimpleObject_thenAnnotationIsNotConsidered() throws IOException {
+        Person person = new Person("John Doe", 30, null);
+        String json = JacksonJrFeatures.objectSerialization(person);
+        assertTrue(json.contains("name"));
+        assertFalse(json.contains("person_name"));
+    }
+
+    @Test
+    public void whenDeserializingJsonObject_thenObjectsAreEqual() throws IOException {
+        Person person = new Person("John Doe", 30, null);
+        String json = JacksonJrFeatures.objectSerialization(person);
+        Person deserializedPerson = JacksonJrFeatures.objectDeserialization(json);
+        assertEquals(person, deserializedPerson);
+    }
+
+    @Test
+    public void whenSerializingWithAnnotations_thenAnnotationIsConsidered() throws IOException {
+        Person person = new Person("John Doe", 30, null);
+        String json = JacksonJrFeatures.objectAnnotationSerialization(person);
+        assertTrue(json.contains("person_name"));
+    }
+
+    @Test
+    public void whenSerializingCustomObject_thenLocalDateIsSerializedAsString() throws IOException {
+        Person person = new Person("John Doe", 30, LocalDate.now());
+        String json = JacksonJrFeatures.customObjectSerialization(person);
+        System.out.println(json);
+        assertTrue(json.contains("birthDate"));
+    }
+
+    @Test
+    public void whenDeserializingCustomObject_thenLocalDateIsDeserialized() throws IOException {
+        Person person = new Person("John Doe", 30, LocalDate.now());
+        String json = JacksonJrFeatures.customObjectSerialization(person);
+        Person deserializedPerson = JacksonJrFeatures.customObjectDeserialization(json);
+        assertEquals(person, deserializedPerson);
+    }
+}

pom.xml

@@ -780,6 +780,7 @@
                 <module>custom-pmd</module>
                 <module>data-structures</module>
                 <module>ddd-contexts</module>
+                <module>jackson-jr</module>
                 <module>jackson-modules</module>
                 <module>jmh</module>
                 <module>deeplearning4j</module>