Homework 8

org/geekhub/Test.java

@@ -6,11 +6,12 @@
 import org.geekhub.storage.Storage;
 
 import java.sql.Connection;
+import java.sql.DriverManager;
 import java.util.List;
 
 public class Test {
     public static void main(String[] args) throws Exception {
-        Connection connection = createConnection("root", "root", "geekdb");
+        Connection connection = createConnection("root", "admin", "geekdb");
 
         Storage storage = new DatabaseStorage(connection);
         List<Cat> cats = storage.list(Cat.class);
@@ -56,7 +57,6 @@ public static void main(String[] args) throws Exception {
     }
 
     private static Connection createConnection(String login, String password, String dbName) throws Exception {
-        //implement me: initiate connection
-        return null;
+        return DriverManager.getConnection("jdbc:mysql://localhost:3306/" + dbName, login, password);
     }
 }

org/geekhub/objects/Cat.java

@@ -1,6 +1,6 @@
 package org.geekhub.objects;
 
-public class Cat {
+public class Cat extends Entity{
     private String name;
     private int age;
 

org/geekhub/objects/User.java

@@ -7,6 +7,8 @@ public class User extends Entity {
     private Integer age;
     private Boolean admin;
     private Double balance;
+
+    @Ignore
     private Date creationDate;
 
     public User() {

org/geekhub/storage/DatabaseStorage.java

@@ -1,9 +1,13 @@
 package org.geekhub.storage;
 
 import org.geekhub.objects.Entity;
+import org.geekhub.objects.Ignore;
+
+import java.lang.reflect.Field;
 import java.sql.*;
-import java.util.List;
-import java.util.Map;
+import java.sql.Connection;
+import java.sql.Statement;
+import java.util.*;
 
 /**
  * Implementation of {@link org.geekhub.storage.Storage} that uses database as a storage for objects.
@@ -21,7 +25,6 @@ public DatabaseStorage(Connection connection) {
 
     @Override
     public <T extends Entity> T get(Class<T> clazz, Integer id) throws Exception {
-        //this method is fully implemented, no need to do anything, it's just an example
         String sql = "SELECT * FROM " + clazz.getSimpleName() + " WHERE id = " + id;
         try(Statement statement = connection.createStatement()) {
             List<T> result = extractResult(clazz, statement.executeQuery(sql));
@@ -31,14 +34,19 @@ public <T extends Entity> T get(Class<T> clazz, Integer id) throws Exception {
 
     @Override
     public <T extends Entity> List<T> list(Class<T> clazz) throws Exception {
-        //implement me according to interface by using extractResult method
-        return null;
+        String sql = "SELECT * FROM " + clazz.getSimpleName();
+        try (Statement statement = connection.createStatement()) {
+            List<T> result = extractResult(clazz, statement.executeQuery(sql));
+            return result.isEmpty() ? Collections.<T>emptyList() : result;
+        }
     }
 
     @Override
     public <T extends Entity> boolean delete(T entity) throws Exception {
-        //implement me
-        return false;
+        String sql = "DELETE FROM " + entity.getClass().getSimpleName() + " WHERE id=" + entity.getId();
+        try (Statement statement = connection.createStatement()) {
+            return 0 != statement.executeUpdate(sql);
+        }
     }
 
     @Override
@@ -47,25 +55,79 @@ public <T extends Entity> void save(T entity) throws Exception {
 
         String sql = null;
         if (entity.isNew()) {
-            //implement me
-            //need to define right SQL query to create object
+            StringBuilder columnName = new StringBuilder();
+            StringBuilder values = new StringBuilder();
+
+            for (Map.Entry<String, Object> entry : data.entrySet()) {
+                columnName.append(entry.getKey()).append(", ");
+                values.append("'").append(entry.getValue()).append("', ");
+            }
+
+            columnName.setLength(columnName.length() - 2);
+            values.setLength(values.length() - 2);
+
+            sql = "INSERT INTO " + entity.getClass().getSimpleName() + " ( " + columnName + " ) VALUES " + " ( " + values + " ) ";
+
         } else {
-            //implement me
-            //need to define right SQL query to update object
+            sql = "UPDATE " + entity.getClass().getSimpleName() + " SET ";
+
+            for (Map.Entry<String, Object> entry : data.entrySet()) {
+               sql += entry.getKey() + " = '" + entry.getValue().toString() + "', ";
+            }
+
+            sql = sql.substring(0, sql.length() - 2);
+            sql += " WHERE id = " + entity.getId();
         }
 
-        //implement me, need to save/update object and update it with new id if it's a creation
+        try (Statement statement  = connection.createStatement()) {
+            statement.executeUpdate(sql);
+
+            if (entity.isNew()) {
+                ResultSet resultSet = statement.getGeneratedKeys();
+                resultSet.next();
+                entity.setId(resultSet.getInt(1));
+            }
+        }
     }
 
     //converts object to map, could be helpful in save method
     private <T extends Entity> Map<String, Object> prepareEntity(T entity) throws Exception {
-        //implement me
-        return null;
+        Map<String, Object> data = new HashMap<>();
+        Field[] fields = entity.getClass().getDeclaredFields();
+
+        for (Field field : fields) {
+            field.setAccessible(true);
+            if (!field.isAnnotationPresent(Ignore.class)) {
+                if (field.getType().equals(Boolean.class)) {
+                    data.put(field.getName(), (Boolean)field.get(entity) ? 1 : 0);
+                } else {
+                    data.put(field.getName(), field.get(entity));
+                }
+            }
+        }
+
+        return data;
     }
 
     //creates list of new instances of clazz by using data from resultset
     private <T extends Entity> List<T> extractResult(Class<T> clazz, ResultSet resultset) throws Exception {
-        //implement me
-        return null;
+        List<T> data = new ArrayList<>();
+        Field[] fields = clazz.getDeclaredFields();
+
+        while (resultset.next()) {
+            T entity = clazz.newInstance();
+            entity.setId(resultset.getInt("id"));
+
+            for (Field field : fields) {
+                field.setAccessible(true);
+                if (!field.isAnnotationPresent(Ignore.class)) {
+                    field.set(entity, resultset.getObject(field.getName()));
+                }
+            }
+
+            data.add(entity);
+        }
+
+        return data;
     }
 }