커스텀 JDBC 라이브러리 만들어 보기

Author: John Grib

src/main/java/core/db/Query.java

@@ -0,0 +1,96 @@
+package core.db;
+
+import util.ReflectionUtil;
+import util.UpperStringMap;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+/**
+ * Query String 을 생성/관리한다.
+ * Created by johngrib on 2017. 4. 22..
+ */
+public class Query {
+
+    private static List<ValueProc> processors = Arrays.asList(new ValueProc[]{
+            new NullProc(),
+            new StringProc(),
+            new IntegerProc()
+    });
+
+    private static String buildAlias(final String key) {
+        return "(?i)" + Pattern.quote("${" + key + "}");
+    }
+
+    /**
+     * query 에 vo 의 값을 set 한다.
+     * query 에서 replace 될 키는 ${key} 의 형태로 지정한다.
+     *
+     * @param sql
+     * @param vo
+     * @return
+     */
+    public static String build(final String sql, final Object vo) {
+        if (vo == null) {
+            return sql;
+        }
+
+        final Map<String, Object> map = ReflectionUtil.objMapper(vo, new UpperStringMap());
+
+        String sourceSql = sql;
+
+        for (final String key : map.keySet()) {
+            final Object val = map.get(key);
+            final String value = processors.stream()
+                    .filter(p -> p.typeCheck(val))
+                    .findFirst().get().proc(val);
+            sourceSql = sourceSql.replaceAll(buildAlias(key), value);
+        }
+        return sourceSql;
+    }
+
+    abstract static class ValueProc {
+        abstract String proc(Object val);
+
+        abstract boolean typeCheck(Object val);
+    }
+
+    static class StringProc extends ValueProc {
+        @Override
+        public String proc(final Object val) {
+            return "'" + String.valueOf(val) + "'";
+        }
+
+        @Override
+        boolean typeCheck(final Object val) {
+            return val instanceof String;
+        }
+    }
+
+    static class NullProc extends ValueProc {
+        @Override
+        public String proc(final Object val) {
+            return "'" + String.valueOf(val) + "'";
+        }
+
+        @Override
+        boolean typeCheck(final Object val) {
+            return val == null;
+        }
+    }
+
+    static class IntegerProc extends ValueProc {
+
+        @Override
+        String proc(final Object val) {
+            return String.valueOf(val);
+        }
+
+        @Override
+        boolean typeCheck(final Object val) {
+            return val instanceof Integer;
+        }
+    }
+}

src/main/java/core/db/ResultData.java

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+package core.db;
+
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.util.*;
+
+/**
+ * ResultSet Wrapper
+ * Created by johngrib on 2017. 4. 22..
+ */
+public class ResultData {
+
+    final private List<String> labels;
+    private ResultSet rs = null;
+
+    public ResultData(final ResultSet rs) throws SQLException {
+        this.rs = rs;
+        this.labels = getColumnLabels(rs);
+    }
+
+    /**
+     * column labels를 리턴한다.
+     * @return
+     */
+    public List<String> getLabels() {
+        return labels;
+    }
+
+    /**
+     * column lable 을 수집한다.
+     * @param rs
+     * @return
+     */
+    private List<String> getColumnLabels(final ResultSet rs) {
+        try {
+            final int size = rs.getMetaData().getColumnCount();
+            final List<String> list = new ArrayList<>(size);
+            final ResultSetMetaData meta = rs.getMetaData();
+
+            for (int i = 1; i <= size; i++) {
+                String name = meta.getColumnName(i);
+                list.add(name);
+            }
+            return list;
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return Collections.EMPTY_LIST;
+    }
+
+    public ResultSet getResultSet() {
+        return rs;
+    }
+
+    public void close() {
+        try {
+            rs.close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        } finally {
+            rs = null;
+        }
+    }
+
+    public boolean next() {
+        try {
+            return rs.next();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return false;
+    }
+
+    public Map<String, Object> getDataMap() {
+        try {
+            final Map<String, Object> data = new HashMap<>();
+            for (String label : labels) {
+                data.put(label, rs.getObject(label));
+            }
+            return data;
+
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return Collections.EMPTY_MAP;
+    }
+}

src/main/java/core/jdbc/JdbcTemplate.java

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+package core.jdbc;
+
+import core.db.Query;
+import core.db.ResultData;
+import util.DataMethod;
+import util.ReflectionUtil;
+import util.UpperStringMap;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.*;
+
+/**
+ * Created by johngrib on 2017. 4. 20..
+ */
+public class JdbcTemplate {
+
+    /**
+     * INSERT, UPDATE 를 수행한다.
+     *
+     * @param sql
+     * @param vo
+     * @throws SQLException
+     */
+    public void update(String sql, Object vo) throws SQLException {
+        Connection con = null;
+        PreparedStatement pstmt = null;
+        try {
+            con = ConnectionManager.getConnection();
+            pstmt = con.prepareStatement(Query.build(sql, vo));
+            pstmt.executeUpdate();
+        } finally {
+            if (pstmt != null) {
+                pstmt.close();
+            }
+
+            if (con != null) {
+                con.close();
+            }
+        }
+    }
+
+    /**
+     * SELECT 를 수행한다.
+     * @param sql
+     * @param voClass
+     * @return
+     * @throws SQLException
+     */
+    public <T> List<T> select(String sql, Class<T> voClass) throws SQLException {
+        return select(sql, voClass, null);
+    }
+
+    /**
+     * SELECT 를 수행한 결과의 첫 번째 row 를 리턴한다.
+     * @param sql
+     * @param voClass
+     * @param vo
+     * @return
+     * @throws SQLException
+     */
+    public <T> T selectOne(String sql, Class<T> voClass, Object vo) throws SQLException {
+        final List<T> list = select(sql, voClass, vo);
+        return (list.size() > 0) ? list.get(0) : null;
+    }
+
+    /**
+     * SELECT 를 수행한다.
+     *
+     * @param sql
+     * @param voClass
+     * @return
+     * @throws SQLException
+     */
+    public <T> List<T> select(String sql, Class<T> voClass, Object vo) throws SQLException {
+
+        ResultSet rs = null;
+        final String query = Query.build(sql, vo);
+        try (
+                final Connection con = ConnectionManager.getConnection();
+                final PreparedStatement pstmt = con.prepareStatement(query);
+        ) {
+            rs = pstmt.executeQuery();
+
+            final ResultData rd = new ResultData(rs);
+            final List<T> list = new ArrayList<>(rs.getFetchSize());
+            final Map<String, DataMethod> setters = ReflectionUtil.getSetterMemberMap(voClass, new UpperStringMap());
+            final List<String> labels = rd.getLabels();
+
+            while (rd.next()) {
+
+                final T row = ReflectionUtil.newSimpleInstance(voClass);
+
+                for (String label: labels) {
+                    DataMethod setter = setters.get(label);
+                    setVoFromResultSet(setter, rd.getResultSet(), row);
+                }
+                list.add(row);
+            }
+            return list;
+        } finally {
+            if (rs != null) {
+                rs.close();
+            }
+        }
+    }
+
+    /**
+     * ResultSet 의 데이터를 vo 에 매핑한다.
+     * @param m
+     * @param rs
+     * @param vo
+     */
+    private void setVoFromResultSet(final DataMethod m, final ResultSet rs, Object vo) {
+        try {
+            if (String.class.equals(m.type)) {
+                m.setter(vo, rs.getString(m.fieldName));
+                return;
+            }
+            if (Integer.class.equals(m.type)) {
+                m.setter(vo, rs.getInt(m.fieldName));
+                return;
+            }
+            if (Double.class.equals(m.type)) {
+                m.setter(vo, rs.getInt(m.fieldName));
+                return;
+            }
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+    }
+}