這是我以前寫的一個系統(tǒng)中自己寫的連個工具,通過看這個代碼你會對Java的泛型和反射有深刻的了解,下面是項目的目錄:
package com.lirui.order.dao.tool;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;public class ResultSetToData { /** * 根據(jù)clazz和ResultSet返回對象(這個對象里的全部屬性)集合 * * @param rs * @param clazz * @return */ public static <T> ArrayList<T> getDataByClassFiled(ResultSet rs, Class<T> clazz) { ArrayList<T> domains = new ArrayList<>(); try { // 獲得自己的屬性 Field[] fields = clazz.getDeclaredFields(); // 獲得父類的屬性 Field[] superFields = clazz.getSuperclass().getDeclaredFields(); // 自己的和父類的屬性相加 Field[] allFields = addFields(fields, superFields); while (rs.next()) { T vo = clazz.newInstance(); // 歷遍所有的屬性 for (Field field : allFields) { String methodName = getSetterMethodName(field.getName()); Method method = clazz .getMethod(methodName, field.getType()); invokeMothod(rs, field, method, vo); } domains.add(vo); } } catch (InstantiationException | IllegalAccessException | SecurityException | SQLException | NoSuchMethodException e) { // TODO Auto-generated catch block e.printStackTrace(); } return domains; } /** * 根據(jù)返回的resultSet來決定生成對象有那些屬性 * * @param rs * @param clazz * @return */ public static <T> ArrayList<T> getDataByResultSet(ResultSet rs, Class<T> clazz) { ArrayList<T> domains = new ArrayList<>(); // 通過metaData獲取到的屬性生成對應(yīng)的FieldList List<Field> allFields = new ArrayList<>(); try { //如果未空值返回 if (null==rs) { return null; } // 先獲取元數(shù)據(jù)再通過元數(shù)據(jù)進行細化的操作 java.sql.ResultSetMetaData metaData = rs.getMetaData(); // 通過ResultSet里面的column的名字來決定用這個類的哪一個Field for (int i = 0; i < metaData.getColumnCount(); i++) { allFields .add(clazz.getDeclaredField(metaData.getColumnName(i+1))); // allFields.add(clazz.getSuperclass().getDeclaredField( // metaData.getColumnName(i+1))); } while (rs.next()) { T vo = clazz.newInstance(); // 歷遍所有的屬性 for (Field field : allFields) { String methodName = getSetterMethodName(field.getName()); Method method = clazz .getMethod(methodName, field.getType()); invokeMothod(rs, field, method, vo); } domains.add(vo); } } catch (InstantiationException | IllegalAccessException | SecurityException | SQLException | NoSuchMethodException | NoSuchFieldException e) { // TODO Auto-generated catch block e.printStackTrace(); } return domains; } /** * 相加f1和f2的Field * * @param f1 * @param f2 * @return */ private static Field[] addFields(Field[] f1, Field[] f2) { List<Field> fields = new ArrayList<>(); for (Field field : f1) { fields.add(field); } for (Field field : f2) { fields.add(field); } return fields.toArray(new Field[f1.length + f2.length]); } /** * 根據(jù)屬性名得到set的方法名 * * @param name * @return */ private static String getSetterMethodName(String name) { String begin = name.substring(0, 1).toUpperCase(); String mothodName = "set" + begin + name.substring(1, name.length()); return mothodName; } /** * 根據(jù)ResultSet和Field的getName從結(jié)果集取出 * * @param rs * @param field * @param method * @param object */ private static void invokeMothod(ResultSet rs, Field field, Method method, Object object) { try { Object o=rs.getObject(field.getName()); method.invoke(object, o); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } }}TansformToSql.java
package com.lirui.order.dao.tool;import java.lang.reflect.Field;public class TransformToSql { /** * 通過反射機制生成插入sql語句 * * @param clazz * @return */ public static String transformToInsertSql(Class<?> clazz) { StringBuffer bufferFront = new StringBuffer(); StringBuffer bufferLast = new StringBuffer(); String tableName = clazz.getSimpleName(); bufferFront.append("insert into " + tableName.substring(0, 1).toLowerCase() + tableName.substring(1, tableName.length()) + "("); bufferLast.append(" values("); // 通過class得到所有的屬性不受訪問控制符空值 Field[] fields = clazz.getDeclaredFields(); for (Field field : fields) { bufferFront.append(field.getName() + ","); bufferLast.append("?,"); } bufferFront.delete(bufferFront.length() - 1, bufferFront.length()); bufferLast.delete(bufferLast.length() - 1, bufferLast.length()); bufferFront.append(")"); bufferLast.append(")"); bufferFront.append(bufferLast); return bufferFront.toString(); } /** * 通過反射機制生成通用的更新語句 * * @param clazz * @return */ public static String transformToUpdateSql(Class<?> clazz) { StringBuffer bufferFront = new StringBuffer(); StringBuffer bufferLast = new StringBuffer(); String tableName = clazz.getSimpleName(); bufferFront.append("update " + tableName.substring(0, 1).toLowerCase() + tableName.substring(1, tableName.length()) + " set "); bufferLast.append(" where id=?"); // 通過class得到所有的屬性不受訪問控制符空值 Field[] fields = clazz.getDeclaredFields(); for (Field field : fields) { if (field.getName().equals("id")) continue; bufferFront.append(field.getName() + "=?,"); } bufferFront.delete(bufferFront.length() - 1, bufferFront.length()); bufferFront.append(bufferLast); return bufferFront.toString(); }}具體意思以后說
