CsvFileToObjectListMapper.java

package com.serioja;

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvParser;
import com.google.common.base.MoreObjects;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;

/*
 depends on Guava and jackson:

 <dependency>
 <groupId>com.fasterxml.jackson.dataformat</groupId>
 <artifactId>jackson-dataformat-csv</artifactId>
 <version>2.4.0</version>
 </dependency>
 */
public class CsvFileToObjectListMapper {

	static class Pojo {
		private String firstName;
		private String lastName;
		private Integer age;

		public String getFirstName() {
			return firstName;
		}

		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}

		public String getLastName() {
			return lastName;
		}

		public void setLastName(String lastName) {
			this.lastName = lastName;
		}

		public Integer getAge() {
			return age;
		}

		public void setAge(Integer age) {
			this.age = age;
		}

		@Override
		public String toString() {
			return MoreObjects.toStringHelper(this.getClass())
					.add("firstName", firstName)
					.add("lastName", lastName)
					.add("age", age).toString();
		}
	}

	interface Testable {

		public Object test(String obj, String columnName) throws Exception;
	}

	private static class IntegerTest implements Testable {

		@Override
		public Integer test(String value, String columnName) throws Exception {
			Integer result = null;
			try {
				result = Integer.valueOf(value);
			} catch (Exception e) {
				throw new IllegalArgumentException("Could not cast to integer: " + value);
			}
			return result;
		}
	}

	private static class StringTest implements Testable {

		private boolean testNotNull = false;
		private Pattern pattern;

		public StringTest() {
		}

		public StringTest(boolean doTestOnNull) {
			this.testNotNull = doTestOnNull;
		}

		public StringTest(String regexp) {
			this.testNotNull = true;
			this.pattern = Pattern.compile(regexp);
		}

		@Override
		public String test(String obj, String columnName) throws Exception {
			if (testNotNull && Strings.isNullOrEmpty(obj)) {
				throw new IllegalArgumentException("Null value received for: " + columnName);
			}
			if (pattern != null) {
				Matcher m = pattern.matcher(obj);
				if (!m.find()) {
					throw new IllegalArgumentException("Pattern not matched for: " + columnName);
				}
			}
			return obj;
		}
	}

	public void test1() throws Exception {

		Map<String, Testable> columnTypes = ImmutableMap.of("age", new IntegerTest(), "firstName", new StringTest(true), "lastName", new StringTest());

		String filePath = "src/main/java/input.csv";

		List<Pojo> pojos = CsvToObjectListMapper.mapToObjects(filePath, columnTypes, Pojo.class);

	}

	public static class CsvToObjectListMapper {

		public static <T> List<T> mapToObjects(String filePath, Map<String, Testable> columnTypes, Class<Pojo> class1) throws Exception {
			CsvMapper mapper = new CsvMapper();
			mapper.enable(CsvParser.Feature.WRAP_AS_ARRAY);
			List<T> resultList = new ArrayList<T>();
			File csvFile = new File(filePath);

			MappingIterator<String[]> reader = mapper.reader(String[].class).readValues(csvFile);

			final String[] headerLine = reader.next();

			String[] nextLine;
			while (reader.hasNext()) {
				nextLine = reader.next();

				Map<String, Object> map = Maps.newHashMap();

				for (int i = 0; i < headerLine.length; i++) {
					String headerName = headerLine[i];
					String value = nextLine[i];
					Testable testable = columnTypes.get(headerName);
					map.put(headerName, testable.test(value, headerName));
				}

				T bean = (T) mapper.convertValue(map, class1);
				resultList.add(bean);
			}
			reader.close();
			return resultList;
		}
	}
}