[原创]通用的面向对象查询的dao（二）
dao的改进版，支持简单的注解，例如@DbConfig(length = 20000,type="BLOB")，其中len为字段长度，type为映射到的类型，支持orm查询和其他查询方式。为sqllite数据库写的。
1.数据源类DataSource：
package com.lowca.robot.dao.support;import java.io.PrintWriter;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;public class DataSource implements javax.sql.DataSource {private static final String DRIVER = "org.sqlite.JDBC";private static final String CONNECT_URL = "jdbc:sqlite:c:/robot.db";private static final String USERNAME = null;private static final String PASSWORD = null;private static final Log log = LogFactory.getLog(DataSource.class);static {try {Class.forName(DRIVER);} catch (ClassNotFoundException e) {throw new RuntimeException("加载JDBC驱动失败:\n" + e.getMessage());}}@Overridepublic Connection getConnection() throws SQLException {Connection conn = DriverManager.getConnection(CONNECT_URL);conn.setAutoCommit(false);return conn;}@Overridepublic Connection getConnection(String username, String password)throws SQLException {Connection conn = DriverManager.getConnection(CONNECT_URL, USERNAME,PASSWORD);conn.setAutoCommit(false);return conn;}@Overridepublic PrintWriter getLogWriter() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic int getLoginTimeout() throws SQLException {// TODO Auto-generated method stubreturn 0;}@Overridepublic void setLogWriter(PrintWriter out) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setLoginTimeout(int seconds) throws SQLException {// TODO Auto-generated method stub}@Overridepublic boolean isWrapperFor(Class<?> iface) throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic <T> T unwrap(Class<T> iface) throws SQLException {// TODO Auto-generated method stubreturn null;}/** * 释放连接 * * @param rs * @param ps * @param conn */public void free(ResultSet rs, PreparedStatement ps, Connection conn) {try {if (rs != null)rs.close();} catch (Exception e) {log.error(this, e);} finally {try {if (ps != null)ps.close();} catch (Exception e) {log.error(this, e);} finally {if (conn != null) {try {conn.close();} catch (SQLException e) {log.error(this, e);}}}}}}package com.lowca.robot.dao.support;import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Inherited;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * 用户自定义标签,带有成员变量的DbConfig */@Documented// 将注释包含在JavaDoc中@Inherited// 允许子类继承父类中的注释。@Target(value = { ElementType.METHOD, ElementType.CONSTRUCTOR })// 标注这个注释使用的范围@Retention(value = RetentionPolicy.RUNTIME)// 要想使用反射得到注释信息，这个注释必须使用public @interface DbConfig {/** * 映射到的数据库类型 * * @return */String type() default "";// 映射到的类型/** * 字段长度 * * @return */int length() default 100;// 字段长度}package com.lowca.robot.dao.support;import java.lang.annotation.Annotation;import java.lang.reflect.Method;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.Date;public class Mapper {/** * 行集映射 * * @param <T> * @param clazz * @param rs * @return * @throws SQLException */public static <T> T rowMapping(Class<T> clazz, ResultSet rs)throws SQLException {T t = null;if (rs.next()) {try {t = clazz.newInstance();} catch (Exception e) {throw new RuntimeException(e);}ResultSetMetaData metadata = rs.getMetaData();int size = metadata.getColumnCount();for (int i = 0; i < size; i++) {String columnName = metadata.getColumnLabel(i + 1);Object columnValue = rs.getObject(metadata.getColumnLabel(i + 1));if (columnValue == null)continue;// 给对象赋值String propertyName = NameConverter.toJavaCase(columnName);String methodName = "set"+ propertyName.substring(0, 1).toUpperCase()+ propertyName.substring(1);Method[] methods = clazz.getMethods();for (Method method : methods) {if (methodName.equals(method.getName())) {try {String propertyTypeName = method.getParameterTypes()[0].getName();String columnTypeName = columnValue.getClass().getName();if (propertyTypeName.equalsIgnoreCase(columnTypeName))method.invoke(t, columnValue);else {// 转换长整型和日期类型的不适配问题if ("java.util.Date".equals(propertyTypeName)&& "java.lang.Long".equals(columnTypeName))method.invoke(t, new Date((Long) columnValue));// 转换整型为布尔型if ("java.lang.Boolean".equals(propertyTypeName)&& "java.lang.Integer".equals(columnTypeName))method.invoke(t, columnValue.toString().equals("0") ? false : true);}} catch (Exception e) {throw new RuntimeException(e);}}}}}return t;}public static String classMapping(Class<?> objectClass,String propertyName, Class<?> propertyClass) {String propertyClassName = propertyClass.getName();if ("java.lang.Integer".equals(propertyClassName)|| "java.lang.Long".equals(propertyClassName)|| "java.lang.Character".equals(propertyClassName)|| "java.lang.Short".equals(propertyClassName))return "INTEGER";if ("java.lang.Float".equals(propertyClassName)|| "java.lang.Double".equals(propertyClassName))return "REAL";if ("java.util.Date".equals(propertyClassName))return "DATETIME";if ("java.lang.Boolean".equals(propertyClassName))return "TINYINT";// String类型需要根据长度来做不同的映射if ("java.lang.String".equals(propertyClassName)) {String methodName = "get"+ propertyName.substring(0, 1).toUpperCase()+ propertyName.substring(1);String typeName = "VARCHAR";try {Annotation[] annotations = objectClass.getDeclaredMethod(methodName).getAnnotations();for (Annotation tag : annotations) {if (tag instanceof DbConfig) {int len = ((DbConfig) tag).length();if (len > 255) {typeName = "TEXT";break;}String type = ((DbConfig) tag).type();return type;}}} catch (Exception e) {throw new RuntimeException(e);}return typeName;}return "";}}package com.lowca.robot.dao.support;/** * <p>一个做命名规范转换的支持类</p> * <p>用来实现在java命名规范和数据库命名规范之间的转换</p> * @author konglz * */public class NameConverter {/** * 数据库命名方式转换成java的命名方式 * * @param s * @return */public static String toJavaCase(String s) {if (s == null || s.trim().length() == 0)return s;StringBuffer sb = new StringBuffer();String[] array = s.split("_");boolean firstTime = true;for (String e : array) {if (e.length() == 0)continue;else if (e.length() == 1)sb.append(!firstTime ? e.toUpperCase() : e);elsesb.append(!firstTime ? (e.substring(0, 1).toUpperCase() + e.substring(1)) : e);firstTime = false;}return sb.toString();}/** * Java命名方式转换成数据库的命名方式 * * @param s * @return */public static String toDbCase(String s) {if (s == null || s.trim().length() == 0)return s;char[] chars = s.toCharArray();boolean firstTime = true;StringBuffer sb = new StringBuffer();for (char c : chars) {if (c >= 'A' && c <= 'Z') {char c1 = (char) (c + 32);sb.append(firstTime ? c1 : "_" + c1);} elsesb.append(c);firstTime = false;}return sb.toString();}public static void main(String[] args) {// System.out// .println(toDbCase("theyBeganToHumWhenSeeingJacksonWalkIntoTheHall"));// System.out// .println(toJavaCase(toDbCase("theyBeganToHumWhenSeeingJacksonWalkIntoTheHall")));StringBuffer sb = new StringBuffer("sdsdfds1");sb.delete(sb.length() - 1, sb.length());System.out.println(sb);}}package com.lowca.robot.dao;import java.lang.reflect.Method;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.lowca.robot.dao.support.DataSource;import com.lowca.robot.dao.support.Mapper;import com.lowca.robot.dao.support.NameConverter;/** * <p> * 通用dao类，用法和说明如下： * </p> * <p> * 1.不支持事务 * </p> * <p> * 2.不支持连接池 * </p> * <p> * 3.命名方法必须严格遵守java pojo和数据库的命名规范/p> * <p> * 4.主键必须叫做“id”，且必须为Integer类型，其他基本类型的属性必须为其封装类型 * </p> * <p> * 5.不支持复杂映射 * </p> * * @author kong * */public class Dao {private final DataSource dataSource = new DataSource();/** * 查询方法 * * @param <T> * @param clazz * @param sql * @param values * @return * @throws SQLException */public <T> T query(Class<T> clazz, String sql, Object[] values)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();T t = Mapper.rowMapping(clazz, rs);dataSource.free(null, ps, conn);return t;}/** * 查询方法（不带参数） * * @param <T> * @param clazz * @param sql * @return * @throws SQLException */public <T> T query(Class<T> clazz, String sql) throws SQLException {return query(clazz, sql, null);}/** * 查询多个对象 * * @param <T> * @param clazz * @param sql * @param values * @return * @throws SQLException */public <T> List<T> queryList(Class<T> clazz, String sql, Object[] values)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();List<T> list = new ArrayList<T>();T t = null;while ((t = Mapper.rowMapping(clazz, rs)) != null) {list.add(t);}dataSource.free(null, ps, conn);return list;}/** * 查询多个对象（不带参数） * * @param <T> * @param clazz * @param sql * @return * @throws SQLException */public <T> List<T> queryList(Class<T> clazz, String sql)throws SQLException {return queryList(clazz, sql, null);}/** * 查询某列第一行的值 * * @param sql * @param values * @param columnName * 列名 * @return * @throws SQLException */public Object queryForObject(String sql, Object[] values, String columnName)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();Object object = null;if (rs.next()) {object = rs.getObject(columnName);}dataSource.free(null, ps, conn);return object;}/** * 查询某列第一行的值（不带参数） * * @param sql * @param columnName * 列名 * @return * @throws SQLException */public Object queryForObject(String sql, String columnName)throws SQLException {return queryForObject(sql, null, columnName);}/** * 查询某列所有行的值作为一个数组返回 * * @param sql * @param values * @param columnName * 列名 * @return * @throws SQLException */public Object[] queryForArray(String sql, Object[] values, String columnName)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();List<Object> list = new ArrayList<Object>();while (rs.next()) {list.add(rs.getObject(columnName));}dataSource.free(null, ps, conn);return list.toArray();}/** * 查询某列所有值作为一个数组返回（不带参数） * * @param sql * @param columnName * @return * @throws SQLException */public Object[] queryForArray(String sql, String columnName)throws SQLException {return queryForArray(sql, null, columnName);}/** * 查询所有行所有列的值，作为一个数组的列表返回 * * @param sql * @param values * @return * @throws SQLException */public List<Object[]> queryForArrayList(String sql, Object[] values)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();List<Object[]> result = new ArrayList<Object[]>();List<Object> list = new ArrayList<Object>();ResultSetMetaData metadata = rs.getMetaData();while (rs.next()) {int size = metadata.getColumnCount();for (int i = 0; i < size; i++) {Object columnValue = rs.getObject(metadata.getColumnLabel(i + 1));list.add(columnValue);}result.add(list.toArray());}dataSource.free(null, ps, conn);return result;}/** * 查询所有行所有列的值，作为一个数组的列表返回（不带参数） * * @param sql * @return * @throws SQLException */public List<Object[]> queryForArrayList(String sql) throws SQLException {return queryForArrayList(sql, null);}/** * 查询成一个map * * @param sql * @param values * @return * @throws SQLException */public Map<String, Object> queryForMap(String sql, Object[] values)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();Map<String, Object> map = new HashMap<String, Object>();ResultSetMetaData metadata = rs.getMetaData();if (rs.next()) {int size = metadata.getColumnCount();for (int i = 0; i < size; i++) {String columnName = metadata.getColumnLabel(i + 1);Object columnValue = rs.getObject(metadata.getColumnLabel(i + 1));map.put(columnName, columnValue);}}dataSource.free(null, ps, conn);return map;}/** * 查询成一个map（不带参数） * * @param sql * @return * @throws SQLException */public Map<String, Object> queryForMap(String sql) throws SQLException {return queryForMap(sql, null);}/** * 查询成一个map的列表 * * @param sql * @param values * @return * @throws SQLException */public List<Map<String, Object>> queryForMapList(String sql, Object[] values)throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();Map<String, Object> map = new HashMap<String, Object>();ResultSetMetaData metadata = rs.getMetaData();if (rs.next()) {int size = metadata.getColumnCount();for (int i = 0; i < size; i++) {String columnName = metadata.getColumnLabel(i + 1);Object columnValue = rs.getObject(metadata.getColumnLabel(i + 1));map.put(columnName, columnValue);}list.add(map);}dataSource.free(null, ps, conn);return list;}/** * 查询成一个map的列表（不带参数） * * @param sql * @return * @throws SQLException */public List<Map<String, Object>> queryForMapList(String sql)throws SQLException {return queryForMapList(sql, null);}/** *统计一类对象的个数 * * @param clazz * @return * @throws SQLException */public int count(Class<?> clazz) throws SQLException {Connection conn = dataSource.getConnection();String tableName = NameConverter.toDbCase(clazz.getSimpleName());String sql = "SELECT COUNT(id) FROM " + tableName;PreparedStatement ps = conn.prepareStatement(sql);ResultSet rs = ps.executeQuery();int num = 0;if (rs.next())num = rs.getInt(1);dataSource.free(null, ps, conn);return num;}/** * 根据sql统计 * * @param sql * @param values * @return * @throws SQLException */public int count(String sql, Object[] values) throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}ResultSet rs = ps.executeQuery();int num = 0;if (rs.next())num = rs.getInt(1);dataSource.free(null, ps, conn);return num;}/** * 根据sql统计（不带参数） * * @param sql * @return * @throws SQLException */public int count(String sql) throws SQLException {return count(sql, null);}/** * 根据id获取 * * @param <T> * @param clazz * @param id * @return * @throws SQLException */public <T> T get(Class<T> clazz, Integer id) throws SQLException {String tableName = NameConverter.toDbCase(clazz.getSimpleName());String sql = "SELECT * FROM " + tableName + " WHERE id="+ id.intValue();Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);ResultSet rs = ps.executeQuery();T t = Mapper.rowMapping(clazz, rs);dataSource.free(null, ps, conn);return t;}/** * 删除对象 * * @param clazz * @param id * @return * @throws SQLException */public int delete(Class<?> clazz, Integer id) throws SQLException {String tableName = NameConverter.toDbCase(clazz.getSimpleName());String sql = "DELETE FROM " + tableName + " WHERE id=" + id.intValue();Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);int rowCount = ps.executeUpdate();dataSource.free(null, ps, conn);return rowCount;}/** * 保存对象 * * @param object * @throws SQLException */public void save(Object object) throws SQLException {// 通过反射提取属性和属性值Method[] methods = object.getClass().getMethods();Map<String, Object> kvMap = new HashMap<String, Object>();for (Method method : methods) {if (method.getName().startsWith("set")) {String key = method.getName().substring(3, 4).toLowerCase()+ method.getName().substring(4);Method getMethod = null;Object value = null;try {getMethod = object.getClass().getDeclaredMethod(method.getName().replaceFirst("set", "get"));value = getMethod.invoke(object);} catch (Exception e) {throw new RuntimeException(e);}kvMap.put(key, value);}}// 生成sqlString tableName = NameConverter.toDbCase(object.getClass().getSimpleName());Object[] values = new Object[kvMap.size()];StringBuffer sb = new StringBuffer("INSERT INTO " + tableName + "(");StringBuffer params = new StringBuffer();int index = 0;for (String key : kvMap.keySet()) {String columnName = NameConverter.toDbCase(key);sb.append(columnName + ",");params.append("?,");values[index] = kvMap.get(key);index++;}if (sb.charAt(sb.length() - 1) == ',')sb.delete(sb.length() - 1, sb.length());if (params.charAt(params.length() - 1) == ',')params.delete(params.length() - 1, params.length());sb.append(") VALUES(").append(params).append(");");String sql = sb.toString();// 执行sqlConnection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}conn.setAutoCommit(true);ps.execute();conn.setAutoCommit(false);// 获取主键ps = conn.prepareStatement("SELECT LAST_INSERT_ROWID()");ResultSet rs = ps.executeQuery();Integer pk = 0;if (rs.next())pk = rs.getInt(1);// 给对象赋主键的值try {Method method = object.getClass().getDeclaredMethod("setId",Integer.class);method.invoke(object, pk);} catch (Exception e) {throw new RuntimeException(e);}dataSource.free(null, ps, conn);}/** * 更新对象 * * @param object * @throws SQLException */public void update(Object object) throws SQLException {// 通过反射提取属性和属性值Method[] methods = object.getClass().getMethods();Map<String, Object> kvMap = new HashMap<String, Object>();for (Method method : methods) {if (method.getName().startsWith("set")) {String key = method.getName().substring(3, 4).toLowerCase()+ method.getName().substring(4);Method getMethod = null;Object value = null;try {getMethod = object.getClass().getDeclaredMethod(method.getName().replaceFirst("set", "get"));value = getMethod.invoke(object);} catch (Exception e) {throw new RuntimeException(e);}kvMap.put(key, value);}}// 生成sqlString tableName = NameConverter.toDbCase(object.getClass().getSimpleName());Object[] values = new Object[kvMap.size()];StringBuffer sb = new StringBuffer("UPDATE " + tableName + " ");int index = 0;Integer id = 0;boolean firstTime = true;for (String key : kvMap.keySet()) {String columnName = NameConverter.toDbCase(key);if (key.equalsIgnoreCase("id")) {id = (Integer) kvMap.get(key);continue;}sb.append((firstTime ? " SET " : "") + columnName + "=?,");firstTime = false;values[index] = kvMap.get(key);index++;}values[index] = id;if (sb.charAt(sb.length() - 1) == ',')sb.delete(sb.length() - 1, sb.length());sb.append(" WHERE id=?;");String sql = sb.toString();// 执行sqlConnection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}conn.setAutoCommit(true);ps.executeUpdate();conn.setAutoCommit(false);dataSource.free(null, ps, conn);}/** * 执行sql语句 * * @param sql * @param values * @return * @throws SQLException */public boolean execute(String sql, Object[] values) throws SQLException {Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);if (values != null) {for (int i = 0; i < values.length; i++) {ps.setObject(i + 1, values[i]);}}conn.setAutoCommit(true);boolean r = ps.execute();conn.setAutoCommit(false);dataSource.free(null, ps, conn);return r;}/** * 执行sql语句，不带参数 * * @param sql * @return * @throws SQLException */public boolean execute(String sql) throws SQLException {return execute(sql, null);}/** * 检查数据库是否有这个表 * * @param clazz * @return * @throws SQLException */public boolean existTable(Class<?> clazz) throws SQLException {String tableName = NameConverter.toDbCase(clazz.getSimpleName());String sql = "SELECT COUNT(*) AS table_count FROM sqlite_master WHERE TYPE='table' AND NAME=?;";Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);ps.setObject(1, tableName);ResultSet rs = ps.executeQuery();int num = 0;if (rs.next()) {num = rs.getInt("table_count");}dataSource.free(null, ps, conn);return num > 0 ? true : false;}/** * 使用类来创建表 * * @param clazz * @param delIfExist * 如果表已存在，true表示删除旧表并重新建表，false表示保留旧表不再重新建 * @throws SQLException */public void createTable(Class<?> clazz, boolean delIfExist)throws SQLException {// 如果表已经存在，则看看是否需要删除boolean existTable = existTable(clazz);if (!delIfExist && existTable) {return;}if (delIfExist && existTable) {deleteTable(clazz);}// 通过反射提取属性和属性值Method[] methods = clazz.getMethods();Map<String, Class<?>> kvMap = new HashMap<String, Class<?>>();for (Method method : methods) {if (method.getName().startsWith("set")) {String property = method.getName().substring(3, 4).toLowerCase()+ method.getName().substring(4);Class<?> propertyClass = method.getParameterTypes()[0];kvMap.put(property, propertyClass);}}// 生成sqlString tableName = NameConverter.toDbCase(clazz.getSimpleName());StringBuffer sb = new StringBuffer("CREATE TABLE " + tableName+ " (id INTEGER PRIMARY KEY,");for (String key : kvMap.keySet()) {if (key.equalsIgnoreCase("id")) {continue;}String columnName = NameConverter.toDbCase(key);Class<?> propertyClass = kvMap.get(key);String dbTypeName = Mapper.classMapping(clazz, key, propertyClass);sb.append(columnName + " " + dbTypeName + ",");}if (sb.charAt(sb.length() - 1) == ',')sb.delete(sb.length() - 1, sb.length());sb.append(");");String sql = sb.toString();System.out.println(sql);// 执行sqlConnection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);conn.setAutoCommit(true);ps.execute();conn.setAutoCommit(false);dataSource.free(null, ps, conn);}/** * 使用sql来建表 * * @param sql * @throws SQLException */public void createTable(String sql) throws SQLException {// 创建表Connection conn = dataSource.getConnection();PreparedStatement ps = conn.prepareStatement(sql);conn.setAutoCommit(true);ps.execute();conn.setAutoCommit(false);dataSource.free(null, ps, conn);}/** * 创建表，如果表已经存在，则不新建 * * @param clazz * @throws SQLException */public void createTable(Class<?> clazz) throws SQLException {createTable(clazz, false);}/** * 按类名删除表 * * @param clazz * @throws SQLException */public void deleteTable(Class<?> clazz) throws SQLException {String tableName = NameConverter.toDbCase(clazz.getSimpleName());String sql = "DROP TABLE IF EXISTS " + tableName;execute(sql);}/** * 按表名删除表 * * @param tableName * @throws SQLException */public void deleteTable(String tableName) throws SQLException {String sql = "DROP TABLE IF EXISTS " + tableName;execute(sql);}/** * 删除所有表 * * @throws SQLException */public int deleteAllTable() throws SQLException {String sql = "SELECT name FROM sqlite_master WHERE TYPE='table';";Object[] objects = queryForArray(sql, "name");int size = objects.length;for (Object o : objects)deleteTable(o.toString());return size;}}