#玩转JDBC打造数据库操作万能工具类JDBCUtil，加入了高效的数据库连接池，利用了参数绑定有效防止SQL注入
在之前学习了MySQL和Oracle之后，那么，如和在Java种去连接这两种数据库。在这个轻量级的工具类当中，使用了数据库连接池 去提高数据库连接的高效性，并且使用了PreparedStatement来执行对SQL的预编译，能够有效防止SQL注入问题。
#一.准备在配置文件配置:配置数据库连接属性文件：在项目新建config包下建立jdbc-mysql.properties并加入以下配置
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8
jdbc.username=root
jdbc.password=root
#二.准备数据库连接池对象：单例
package util;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.mchange.v2.c3p0.DataSources;
import java.beans.PropertyVetoException;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
/**
* 数据库连接对象
* Created by yuandl on 2016-12-16.
*/
public class DBConnectionPool {
private static volatile DBConnectionPool dbConnection;
private ComboPooledDataSource cpds;
/**
* 在构造函数初始化的时候获取数据库连接
*/
private DBConnectionPool() {
try {
/**通过属性文件获取数据库连接的参数值**/
Properties properties = new Properties();
FileInputStream fileInputStream = new FileInputStream("src/config/jdbc-mysql.properties");
properties.load(fileInputStream);
/**获取属性文件中的值**/
String driverClassName = properties.getProperty("jdbc.driverClassName");
String url = properties.getProperty("jdbc.url");
String username = properties.getProperty("jdbc.username");
String password = properties.getProperty("jdbc.password");
/**数据库连接池对象**/
cpds = new ComboPooledDataSource();
/**设置数据库连接驱动**/
cpds.setDriverClass(driverClassName);
/**设置数据库连接地址**/
cpds.setJdbcUrl(url);
/**设置数据库连接用户名**/
cpds.setUser(username);
/**设置数据库连接密码**/
cpds.setPassword(password);
/**初始化时创建的连接数,应在minPoolSize与maxPoolSize之间取值.默认为3**/
cpds.setInitialPoolSize(3);
/**连接池中保留的最大连接数据.默认为15**/
cpds.setMaxPoolSize(10);
/**当连接池中的连接用完时，C3PO一次性创建新的连接数目;**/
cpds.setAcquireIncrement(1);
/**隔多少秒检查所有连接池中的空闲连接,默认为0表示不检查;**/
cpds.setIdleConnectionTestPeriod(60);
/**最大空闲时间,超过空闲时间的连接将被丢弃.为0或负数据则永不丢弃.默认为0;**/
cpds.setMaxIdleTime(3000);
/**因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交的
时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable
等方法来提升连接测试的性能。Default: false**/
cpds.setTestConnectionOnCheckout(true);
/**如果设为true那么在取得连接的同时将校验连接的有效性。Default: false **/
cpds.setTestConnectionOnCheckin(true);
/**定义在从数据库获取新的连接失败后重复尝试获取的次数，默认为30;**/
cpds.setAcquireRetryAttempts(30);
/**两次连接中间隔时间默认为1000毫秒**/
cpds.setAcquireRetryDelay(1000);
/** 获取连接失败将会引起所有等待获取连接的线程异常,
但是数据源仍有效的保留,并在下次调用getConnection()的时候继续尝试获取连接.如果设为true,
那么尝试获取连接失败后该数据源将申明已经断开并永久关闭.默认为false**/
cpds.setBreakAfterAcquireFailure(true);
} catch (IOException e) {
e.printStackTrace();
} catch (PropertyVetoException e) {
e.printStackTrace();
}
}
/**
* 获取数据库连接对象，单例
*
* @return
*/
public static DBConnectionPool getInstance() {
if (dbConnection == null) {
synchronized (DBConnectionPool.class) {
if (dbConnection == null) {
dbConnection = new DBConnectionPool();
}
}
}
return dbConnection;
}
/**
* 获取数据库连接
*
* @return 数据库连接
*/
public final synchronized Connection getConnection() throws SQLException {
return cpds.getConnection();
}
/**
* finalize()方法是在垃圾收集器删除对象之前对这个对象调用的。
*
* @throws Throwable
*/
protected void finalize() throws Throwable {
DataSources.destroy(cpds);
super.finalize();
}
}#三.实现新增、修改、删除、查询操作的两个核心方法：可以实现任何复杂的SQL,而且通过数据绑定的方式不会有SQL注入问题
/**
* 可以执行新增，修改，删除
*
* @param sql sql语句
* @param bindArgs 绑定参数
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int executeUpdate(String sql, Object[] bindArgs) throws SQLException {
/**影响的行数**/
int affectRowCount = -1;
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
/**从数据库连接池中获取数据库连接**/
connection = DBConnectionPool.getInstance().getConnection();
/**执行SQL预编译**/
preparedStatement = connection.prepareStatement(sql.toString());
/**设置不自动提交，以便于在出现异常的时候数据库回滚**/
connection.setAutoCommit(false);
System.out.println(getExecSQL(sql, bindArgs));
if (bindArgs != null) {
/**绑定参数设置sql占位符中的值**/
for (int i = 0; i < bindArgs.length; i++) {
preparedStatement.setObject(i + 1, bindArgs[i]);
}
}
/**执行sql**/
affectRowCount = preparedStatement.executeUpdate();
connection.commit();
String operate;
if (sql.toUpperCase().indexOf("DELETE FROM") != -1) {
operate = "删除";
} else if (sql.toUpperCase().indexOf("INSERT INTO") != -1) {
operate = "新增";
} else {
operate = "修改";
}
System.out.println("成功" + operate + "了" + affectRowCount + "行");
System.out.println();
} catch (Exception e) {
if (connection != null) {
connection.rollback();
}
e.printStackTrace();
throw e;
} finally {
if (preparedStatement != null) {
preparedStatement.close();
}
if (connection != null) {
connection.close();
}
}
return affectRowCount;
}
/**
* 执行查询
*
* @param sql 要执行的sql语句
* @param bindArgs 绑定的参数
* @return List<Map<String, Object>>结果集对象
* @throws SQLException SQL执行异常
*/
public static List<Map<String, Object>> executeQuery(String sql, Object[] bindArgs) throws SQLException {
List<Map<String, Object>> datas = new ArrayList<>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
/**获取数据库连接池中的连接**/
connection = DBConnectionPool.getInstance().getConnection();
preparedStatement = connection.prepareStatement(sql);
if (bindArgs != null) {
/**设置sql占位符中的值**/
for (int i = 0; i < bindArgs.length; i++) {
preparedStatement.setObject(i + 1, bindArgs[i]);
}
}
System.out.println(getExecSQL(sql, bindArgs));
/**执行sql语句，获取结果集**/
resultSet = preparedStatement.executeQuery();
getDatas(resultSet);
System.out.println();
} catch (Exception e) {
e.printStackTrace();
throw e;
} finally {
if (resultSet != null) {
resultSet.close();
}
if (preparedStatement != null) {
preparedStatement.close();
}
if (connection != null) {
connection.close();
}
}
return datas;
}#四.执行新增的简化操作
/**
* 执行数据库插入操作
*
* @param valueMap 插入数据表中key为列名和value为列对应的值的Map对象
* @param tableName 要插入的数据库的表名
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int insert(String tableName, Map<String, Object> valueMap) throws SQLException {
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = valueMap.keySet();
Iterator<String> iterator = keySet.iterator();
/**要插入的字段sql，其实就是用key拼起来的**/
StringBuilder columnSql = new StringBuilder();
/**要插入的字段值，其实就是？**/
StringBuilder unknownMarkSql = new StringBuilder();
Object[] bindArgs = new Object[valueMap.size()];
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
columnSql.append(i == 0 ? "" : ",");
columnSql.append(key);
unknownMarkSql.append(i == 0 ? "" : ",");
unknownMarkSql.append("?");
bindArgs[i] = valueMap.get(key);
i++;
}
/**开始拼插入的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("INSERT INTO ");
sql.append(tableName);
sql.append(" (");
sql.append(columnSql);
sql.append(" ) VALUES (");
sql.append(unknownMarkSql);
sql.append(" )");
return executeUpdate(sql.toString(), bindArgs);
}#五.执行更新的简化操作
/**
* 执行更新操作
*
* @param tableName 表名
* @param valueMap 要更改的值
* @param whereMap 条件
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int update(String tableName, Map<String, Object> valueMap, Map<String, Object> whereMap) throws SQLException {
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = valueMap.keySet();
Iterator<String> iterator = keySet.iterator();
/**开始拼插入的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("UPDATE ");
sql.append(tableName);
sql.append(" SET ");
/**要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder columnSql = new StringBuilder();
int i = 0;
List<Object> objects = new ArrayList<>();
while (iterator.hasNext()) {
String key = iterator.next();
columnSql.append(i == 0 ? "" : ",");
columnSql.append(key + " = ? ");
objects.add(valueMap.get(key));
i++;
}
sql.append(columnSql);
/**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder whereSql = new StringBuilder();
int j = 0;
if (whereMap != null && whereMap.size() > 0) {
whereSql.append(" WHERE ");
iterator = whereMap.keySet().iterator();
while (iterator.hasNext()) {
String key = iterator.next();
whereSql.append(j == 0 ? "" : " AND ");
whereSql.append(key + " = ? ");
objects.add(whereMap.get(key));
j++;
}
sql.append(whereSql);
}
return executeUpdate(sql.toString(), objects.toArray());
}#六.执行删除的简化操作
/**
* 执行删除操作
*
* @param tableName 要删除的表名
* @param whereMap 删除的条件
* @return 影响的行数
* @throws SQLException SQL执行异常
*/
public static int delete(String tableName, Map<String, Object> whereMap) throws SQLException {
/**准备删除的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("DELETE FROM ");
sql.append(tableName);
/**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder whereSql = new StringBuilder();
Object[] bindArgs = null;
if (whereMap != null && whereMap.size() > 0) {
bindArgs = new Object[whereMap.size()];
whereSql.append(" WHERE ");
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = whereMap.keySet();
Iterator<String> iterator = keySet.iterator();
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
whereSql.append(i == 0 ? "" : " AND ");
whereSql.append(key + " = ? ");
bindArgs[i] = whereMap.get(key);
i++;
}
sql.append(whereSql);
}
return executeUpdate(sql.toString(), bindArgs);
}#七.查询的4种玩法
- 1.执行sql通过 Map<String, Object>限定查询条件查询
/**
* 1..执行sql通过 Map<String, Object>限定查询条件查询
*
* @param tableName 表名
* @param whereMap where条件
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
Map<String, Object> whereMap) throws SQLException {
String whereClause = "";
Object[] whereArgs = null;
if (whereMap != null && whereMap.size() > 0) {
Iterator<String> iterator = whereMap.keySet().iterator();
whereArgs = new Object[whereMap.size()];
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
whereClause += (i == 0 ? "" : " AND ");
whereClause += (key + " = ? ");
whereArgs[i] = whereMap.get(key);
i++;
}
}
return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
}- 2.执行sql条件参数绑定形式的查询
/**
* 2.执行sql条件参数绑定形式的查询
*
* @param tableName 表名
* @param whereClause where条件的sql
* @param whereArgs where条件中占位符中的值
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
String whereClause,
String[] whereArgs) throws SQLException {
return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
}- 3.包含所有的查询条件的查询方法
/**
* 执行全部结构的sql查询
*
* @param tableName 表名
* @param distinct 去重
* @param columns 要查询的列名
* @param selection where条件
* @param selectionArgs where条件中占位符中的值
* @param groupBy 分组
* @param having 筛选
* @param orderBy 排序
* @param limit 分页
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
boolean distinct,
String[] columns,
String selection,
Object[] selectionArgs,
String groupBy,
String having,
String orderBy,
String limit) throws SQLException {
String sql = buildQueryString(distinct, tableName, columns, selection, groupBy, having, orderBy, limit);
return executeQuery(sql, selectionArgs);
}- 4.通过单纯的sql查询数据,慎用，会有sql注入问题，只是为了方便查询，实际开发中不会去使用这个方法
* 4.通过sql查询数据,
* 慎用，会有sql注入问题只是为了方便查询，实际开发中不会去使用这个方法
*
* @param sql
* @return 查询的数据集合
* @throws SQLException
*/
public static List<Map<String, Object>> query(String sql) throws SQLException {
return executeQuery(sql, null);
}#八.DBUtil的完整代码
package util;
import com.sun.istack.internal.Nullable;
import java.sql.*;
import java.util.*;
import java.util.regex.Pattern;
/**
* 数据库JDBC连接工具类
* Created by yuandl on 2016-12-16.
*/
public class DBUtil {
/**
* 执行数据库插入操作
*
* @param valueMap 插入数据表中key为列名和value为列对应的值的Map对象
* @param tableName 要插入的数据库的表名
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int insert(String tableName, Map<String, Object> valueMap) throws SQLException {
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = valueMap.keySet();
Iterator<String> iterator = keySet.iterator();
/**要插入的字段sql，其实就是用key拼起来的**/
StringBuilder columnSql = new StringBuilder();
/**要插入的字段值，其实就是？**/
StringBuilder unknownMarkSql = new StringBuilder();
Object[] bindArgs = new Object[valueMap.size()];
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
columnSql.append(i == 0 ? "" : ",");
columnSql.append(key);
unknownMarkSql.append(i == 0 ? "" : ",");
unknownMarkSql.append("?");
bindArgs[i] = valueMap.get(key);
i++;
}
/**开始拼插入的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("INSERT INTO ");
sql.append(tableName);
sql.append(" (");
sql.append(columnSql);
sql.append(" ) VALUES (");
sql.append(unknownMarkSql);
sql.append(" )");
return executeUpdate(sql.toString(), bindArgs);
}
/**
* 执行更新操作
*
* @param tableName 表名
* @param valueMap 要更改的值
* @param whereMap 条件
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int update(String tableName, Map<String, Object> valueMap, Map<String, Object> whereMap) throws SQLException {
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = valueMap.keySet();
Iterator<String> iterator = keySet.iterator();
/**开始拼插入的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("UPDATE ");
sql.append(tableName);
sql.append(" SET ");
/**要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder columnSql = new StringBuilder();
int i = 0;
List<Object> objects = new ArrayList<>();
while (iterator.hasNext()) {
String key = iterator.next();
columnSql.append(i == 0 ? "" : ",");
columnSql.append(key + " = ? ");
objects.add(valueMap.get(key));
i++;
}
sql.append(columnSql);
/**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder whereSql = new StringBuilder();
int j = 0;
if (whereMap != null && whereMap.size() > 0) {
whereSql.append(" WHERE ");
iterator = whereMap.keySet().iterator();
while (iterator.hasNext()) {
String key = iterator.next();
whereSql.append(j == 0 ? "" : " AND ");
whereSql.append(key + " = ? ");
objects.add(whereMap.get(key));
j++;
}
sql.append(whereSql);
}
return executeUpdate(sql.toString(), objects.toArray());
}
/**
* 执行删除操作
*
* @param tableName 要删除的表名
* @param whereMap 删除的条件
* @return 影响的行数
* @throws SQLException SQL执行异常
*/
public static int delete(String tableName, Map<String, Object> whereMap) throws SQLException {
/**准备删除的sql语句**/
StringBuilder sql = new StringBuilder();
sql.append("DELETE FROM ");
sql.append(tableName);
/**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
StringBuilder whereSql = new StringBuilder();
Object[] bindArgs = null;
if (whereMap != null && whereMap.size() > 0) {
bindArgs = new Object[whereMap.size()];
whereSql.append(" WHERE ");
/**获取数据库插入的Map的键值对的值**/
Set<String> keySet = whereMap.keySet();
Iterator<String> iterator = keySet.iterator();
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
whereSql.append(i == 0 ? "" : " AND ");
whereSql.append(key + " = ? ");
bindArgs[i] = whereMap.get(key);
i++;
}
sql.append(whereSql);
}
return executeUpdate(sql.toString(), bindArgs);
}
/**
* 可以执行新增，修改，删除
*
* @param sql sql语句
* @param bindArgs 绑定参数
* @return 影响的行数
* @throws SQLException SQL异常
*/
public static int executeUpdate(String sql, Object[] bindArgs) throws SQLException {
/**影响的行数**/
int affectRowCount = -1;
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
/**从数据库连接池中获取数据库连接**/
connection = DBConnectionPool.getInstance().getConnection();
/**执行SQL预编译**/
preparedStatement = connection.prepareStatement(sql.toString());
/**设置不自动提交，以便于在出现异常的时候数据库回滚**/
connection.setAutoCommit(false);
System.out.println(getExecSQL(sql, bindArgs));
if (bindArgs != null) {
/**绑定参数设置sql占位符中的值**/
for (int i = 0; i < bindArgs.length; i++) {
preparedStatement.setObject(i + 1, bindArgs[i]);
}
}
/**执行sql**/
affectRowCount = preparedStatement.executeUpdate();
connection.commit();
String operate;
if (sql.toUpperCase().indexOf("DELETE FROM") != -1) {
operate = "删除";
} else if (sql.toUpperCase().indexOf("INSERT INTO") != -1) {
operate = "新增";
} else {
operate = "修改";
}
System.out.println("成功" + operate + "了" + affectRowCount + "行");
System.out.println();
} catch (Exception e) {
if (connection != null) {
connection.rollback();
}
e.printStackTrace();
throw e;
} finally {
if (preparedStatement != null) {
preparedStatement.close();
}
if (connection != null) {
connection.close();
}
}
return affectRowCount;
}
/**
* 通过sql查询数据,
* 慎用，会有sql注入问题
*
* @param sql
* @return 查询的数据集合
* @throws SQLException
*/
public static List<Map<String, Object>> query(String sql) throws SQLException {
return executeQuery(sql, null);
}
/**
* 执行sql通过 Map<String, Object>限定查询条件查询
*
* @param tableName 表名
* @param whereMap where条件
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
Map<String, Object> whereMap) throws SQLException {
String whereClause = "";
Object[] whereArgs = null;
if (whereMap != null & whereMap.size() > 0) {
Iterator<String> iterator = whereMap.keySet().iterator();
whereArgs = new Object[whereMap.size()];
int i = 0;
while (iterator.hasNext()) {
String key = iterator.next();
whereClause += (i == 0 ? "" : " AND ");
whereClause += (key + " = ? ");
whereArgs[i] = whereMap.get(key);
i++;
}
}
return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
}
/**
* 执行sql条件参数绑定形式的查询
*
* @param tableName 表名
* @param whereClause where条件的sql
* @param whereArgs where条件中占位符中的值
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
String whereClause,
String[] whereArgs) throws SQLException {
return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
}
/**
* 执行全部结构的sql查询
*
* @param tableName 表名
* @param distinct 去重
* @param columns 要查询的列名
* @param selection where条件
* @param selectionArgs where条件中占位符中的值
* @param groupBy 分组
* @param having 筛选
* @param orderBy 排序
* @param limit 分页
* @return List<Map<String, Object>>
* @throws SQLException
*/
public static List<Map<String, Object>> query(String tableName,
boolean distinct,
String[] columns,
String selection,
Object[] selectionArgs,
String groupBy,
String having,
String orderBy,
String limit) throws SQLException {
String sql = buildQueryString(distinct, tableName, columns, selection, groupBy, having, orderBy, limit);
return executeQuery(sql, selectionArgs);
}
/**
* 执行查询
*
* @param sql 要执行的sql语句
* @param bindArgs 绑定的参数
* @return List<Map<String, Object>>结果集对象
* @throws SQLException SQL执行异常
*/
public static List<Map<String, Object>> executeQuery(String sql, Object[] bindArgs) throws SQLException {
List<Map<String, Object>> datas = new ArrayList<>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
/**获取数据库连接池中的连接**/
connection = DBConnectionPool.getInstance().getConnection();
preparedStatement = connection.prepareStatement(sql);
if (bindArgs != null) {
/**设置sql占位符中的值**/
for (int i = 0; i < bindArgs.length; i++) {
preparedStatement.setObject(i + 1, bindArgs[i]);
}
}
System.out.println(getExecSQL(sql, bindArgs));
/**执行sql语句，获取结果集**/
resultSet = preparedStatement.executeQuery();
getDatas(resultSet);
System.out.println();
} catch (Exception e) {
e.printStackTrace();
throw e;
} finally {
if (resultSet != null) {
resultSet.close();
}
if (preparedStatement != null) {
preparedStatement.close();
}
if (connection != null) {
connection.close();
}
}
return datas;
}
/**
* 将结果集对象封装成List<Map<String, Object>> 对象
*
* @param resultSet 结果多想
* @return 结果的封装
* @throws SQLException
*/
private static List<Map<String, Object>> getDatas(ResultSet resultSet) throws SQLException {
List<Map<String, Object>> datas = new ArrayList<>();
/**获取结果集的数据结构对象**/
ResultSetMetaData metaData = resultSet.getMetaData();
while (resultSet.next()) {
Map<String, Object> rowMap = new HashMap<>();
for (int i = 1; i <= metaData.getColumnCount(); i++) {
rowMap.put(metaData.getColumnName(i), resultSet.getObject(i));
}
datas.add(rowMap);
}
System.out.println("成功查询到了" + datas.size() + "行数据");
for (int i = 0; i < datas.size(); i++) {
Map<String, Object> map = datas.get(i);
System.out.println("第" + (i + 1) + "行：" + map);
}
return datas;
}
/**
* Build an SQL query string from the given clauses.
*
* @param distinct true if you want each row to be unique, false otherwise.
* @param tables The table names to compile the query against.
* @param columns A list of which columns to return. Passing null will
* return all columns, which is discouraged to prevent reading
* data from storage that isn't going to be used.
* @param where A filter declaring which rows to return, formatted as an SQL
* WHERE clause (excluding the WHERE itself). Passing null will
* return all rows for the given URL.
* @param groupBy A filter declaring how to group rows, formatted as an SQL
* GROUP BY clause (excluding the GROUP BY itself). Passing null
* will cause the rows to not be grouped.
* @param having A filter declare which row groups to include in the cursor,
* if row grouping is being used, formatted as an SQL HAVING
* clause (excluding the HAVING itself). Passing null will cause
* all row groups to be included, and is required when row
* grouping is not being used.
* @param orderBy How to order the rows, formatted as an SQL ORDER BY clause
* (excluding the ORDER BY itself). Passing null will use the
* default sort order, which may be unordered.
* @param limit Limits the number of rows returned by the query,
* formatted as LIMIT clause. Passing null denotes no LIMIT clause.
* @return the SQL query string
*/
private static String buildQueryString(
boolean distinct, String tables, String[] columns, String where,
String groupBy, String having, String orderBy, String limit) {
if (isEmpty(groupBy) && !isEmpty(having)) {
throw new IllegalArgumentException(
"HAVING clauses are only permitted when using a groupBy clause");
}
if (!isEmpty(limit) && !sLimitPattern.matcher(limit).matches()) {
throw new IllegalArgumentException("invalid LIMIT clauses:" + limit);
}
StringBuilder query = new StringBuilder(120);
query.append("SELECT ");
if (distinct) {
query.append("DISTINCT ");
}
if (columns != null && columns.length != 0) {
appendColumns(query, columns);
} else {
query.append(" * ");
}
query.append("FROM ");
query.append(tables);
appendClause(query, " WHERE ", where);
appendClause(query, " GROUP BY ", groupBy);
appendClause(query, " HAVING ", having);
appendClause(query, " ORDER BY ", orderBy);
appendClause(query, " LIMIT ", limit);
return query.toString();
}
/**
* Add the names that are non-null in columns to s, separating
* them with commas.
*/
private static void appendColumns(StringBuilder s, String[] columns) {
int n = columns.length;
for (int i = 0; i < n; i++) {
String column = columns[i];
if (column != null) {
if (i > 0) {
s.append(", ");
}
s.append(column);
}
}
s.append(' ');
}
/**
* addClause
*
* @param s the add StringBuilder
* @param name clauseName
* @param clause clauseSelection
*/
private static void appendClause(StringBuilder s, String name, String clause) {
if (!isEmpty(clause)) {
s.append(name);
s.append(clause);
}
}
/**
* Returns true if the string is null or 0-length.
*
* @param str the string to be examined
* @return true if str is null or zero length
*/
private static boolean isEmpty(@Nullable CharSequence str) {
if (str == null || str.length() == 0)
return true;
else
return false;
}
/**
* the pattern of limit
*/
private static final Pattern sLimitPattern =
Pattern.compile("\\s*\\d+\\s*(,\\s*\\d+\\s*)?");
/**
* After the execution of the complete SQL statement, not necessarily the actual implementation of the SQL statement
*
* @param sql SQL statement
* @param bindArgs Binding parameters
* @return Replace? SQL statement executed after the
*/
private static String getExecSQL(String sql, Object[] bindArgs) {
StringBuilder sb = new StringBuilder(sql);
if (bindArgs != null && bindArgs.length > 0) {
int index = 0;
for (int i = 0; i < bindArgs.length; i++) {
index = sb.indexOf("?", index);
sb.replace(index, index + 1, String.valueOf(bindArgs[i]));
}
}
return sb.toString();
}
}#九.用法
- 测试代码
import util.DBUtil;
import java.sql.SQLException;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Created by yuandl on 2016-12-16.
*/
public class DBTest {
public static void main(String[] args) {
System.out.println("数据库的原数据");
testQuery3();
testInsert();
System.out.println("执行插入后的数据");
testQuery3();
testUpdate();
System.out.println("执行修改后的数据");
testQuery3();
testDelete();
System.out.println("执行删除后的数据");
testQuery3();
System.out.println("带条件的查询1");
testQuery2();
System.out.println("带条件的查询2");
testQuery1();
}
/**
* 测试插入
*/
private static void testInsert() {
Map<String, Object> map = new HashMap<>();
map.put("emp_id", 1013);
map.put("name", "JDBCUtil测试");
map.put("job", "developer");
map.put("salary", 10000);
map.put("hire_date", new java.sql.Date(System.currentTimeMillis()));
try {
int count = DBUtil.insert("emp_test", map);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 测试更新
*/
private static void testUpdate() {
Map<String, Object> map = new HashMap<>();
map.put("name", "测试更新");
Map<String, Object> whereMap = new HashMap<>();
whereMap.put("emp_id", "1013");
try {
int count = DBUtil.update("emp_test", map, whereMap);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 测试删除
*/
private static void testDelete() {
Map<String, Object> whereMap = new HashMap<>();
whereMap.put("emp_id", 1013);
whereMap.put("job", "developer");
try {
int count = DBUtil.delete("emp_test", whereMap);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 查询方式一
*/
public static void testQuery1() {
Map<String,Object> whereMap=new HashMap<>();
whereMap.put("salary","10000");
try {
DBUtil.query("emp_test",whereMap);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 查询方式二
*/
public static void testQuery2() {
String where = "job = ? AND salary = ? ";
String[] whereArgs = new String[]{"clerk", "3000"};
try {
List<Map<String, Object>> list = DBUtil.query("emp_test", where, whereArgs);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 查询方式三
*/
public static void testQuery3() {
try {
List<Map<String, Object>> list = DBUtil.query("emp_test", false, null, null, null, null, null, null, null);
} catch (SQLException e) {
e.printStackTrace();
}
}
}- 打印结果
数据库的原数据
SELECT * FROM emp_test
成功查询到了14行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
INSERT INTO emp_test (name,hire_date,job,salary,emp_id ) VALUES (JDBCUtil测试,2016-12-17,developer,10000,1013 )
成功新增了1行
执行插入后的数据
SELECT * FROM emp_test
成功查询到了15行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
第15行：{DEPT_TEST_ID=null, EMP_ID=1013, SALARY=10000, HIRE_DATE=2016-12-17, BONUS=null, MANAGER=null, JOB=developer, NAME=JDBCUtil测试}
UPDATE emp_test SET name = 测试更新 WHERE emp_id = 1013
成功修改了1行
执行修改后的数据
SELECT * FROM emp_test
成功查询到了15行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
第15行：{DEPT_TEST_ID=null, EMP_ID=1013, SALARY=10000, HIRE_DATE=2016-12-17, BONUS=null, MANAGER=null, JOB=developer, NAME=测试更新}
DELETE FROM emp_test WHERE job = developer AND emp_id = 1013
成功删除了1行
执行删除后的数据
SELECT * FROM emp_test
成功查询到了14行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
带条件的查询1
SELECT * FROM emp_test WHERE job = clerk AND salary = 3000
成功查询到了1行数据
第1行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
带条件的查询2
SELECT * FROM emp_test WHERE salary = 10000
成功查询到了1行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
#十.GitHub
React
Typescript
Django
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Facebook
Microsoft
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D3
Tencent