Query encapsulation-reflection and jdbc encapsulation reflection in jdbc

Query encapsulation-reflection and jdbc encapsulation reflection in jdbc

Query statements are similar when native jdbc is used. Therefore, reflection is used to encapsulate the query statements in jdbc.

Query a single statement
Query multiple statements

Package src. jdbcTest; import java. lang. reflect. field; import java. SQL. connection; import java. SQL. driverManager; import java. SQL. preparedStatement; import java. SQL. resultSet; import java. SQL. resultSetMetaData; import java. SQL. SQLException; import java. util. arrayList; import java. util. list; import org. apache. log4j. logger;/***** @ author chencong * @ Time 12:37:55 on January 1, August 3, 2017 * @ TODO returns single and multi-row records through reflection */public cl Ass DBUtils {private static final String DRIVER_URL = "jdbc: sqlserver: // localhost: 1433; DataBaseName = mangerQQSys"; private static final String DRIVER_NAME = "com. microsoft. sqlserver. jdbc. SQLServerDriver "; private static final String DB_USER =" sa "; private static final String DB_PASSWORD =" 123456 "; private Connection connection = null; private PreparedStatement preparedStatement = null; private R EsultSet resultSet = null; public DBUtils () {}{ try {Class. forName (DRIVER_NAME); connection = DriverManager. getConnection (DRIVER_URL, DB_USER, DB_PASSWORD);} catch (ClassNotFoundException e) {e. printStackTrace ();} catch (SQLException e) {e. printStackTrace () ;}} public Connection getConnection () {return connection;}/*** close database connection ** @ param Connection * @ param ptStatement * @ param resultS Et */public void closeAll (Connection connection, PreparedStatement ptStatement, ResultSet resultSet) {try {if (connection! = Null) {connection. close () ;}if (ptStatement! = Null) {ptStatement. close ();} if (resultSet! = Null) {ptStatement. close () ;}} catch (SQLException e) {e. printStackTrace () ;}}/*** close database connection ** @ param ptStatement * @ param resultSet */public void closeAll (PreparedStatement ptStatement, ResultSet resultSet) {try {if (ptStatement! = Null) {ptStatement. close ();} if (resultSet! = Null) {ptStatement. close () ;}} catch (SQLException e) {e. printStackTrace ();}} /*** the reflection mechanism returns a single record T ** @ param SQL * @ param params * @ param clazz * @ return * @ throws Exception */public <T> T selectSimpleResult (String SQL, list <Object> params, Class <T> clazz) throws Exception {if (connection = null) {return null;} if (SQL = null | clazz = null) {return null;} T resultObject = null; in T index = 1; preparedStatement = connection. prepareStatement (SQL); if (params! = Null &&! Params. isEmpty () {for (int I = 0; I <params. size (); I ++) {preparedStatement. setObject (index, params. get (I); index ++ ;}} resultSet = preparedStatement.exe cuteQuery (); ResultSetMetaData metaData = resultSet. getMetaData (); int couLength = metaData. getColumnCount (); while (resultSet. next () {// reflection to a generic object resultObject = clazz. newInstance (); for (int I = 0; I <couLength; I ++) {String colName = MetaData. getColumnName (I + 1); Object colValue = resultSet. getObject (colName); if (colValue = null) {colValue = "";} Field field = clazz. getDeclaredField (colName); field. setAccessible (true); // cancel the Java check mechanism to open the access permission field. set (resultObject, colValue) ;}return resultObject ;} /*** query multiple records ** @ param SQL * the SQL statement to be executed * @ param params * @ param clazz * @ return * @ throws Exception */public <T> list <T> selectMoreResult (String SQL, List <Object> params, Class <T> clazz) throws Exception {if (connection = null) {return null ;} if (SQL = null | clazz = null) {return null;} List <T> list = new ArrayList <T> (); int index = 1; preparedStatement = connection. prepareStatement (SQL); if (params! = Null &&! Params. isEmpty () {for (int I = 0; I <params. size (); I ++) {System. out. println (index + ":" + params. get (I); preparedStatement. setObject (index, params. get (I); index ++ ;}} resultSet = preparedStatement.exe cuteQuery (); ResultSetMetaData metaData = resultSet. getMetaData (); int colLength = metaData. getColumnCount (); while (resultSet. next () {// create object T resultObject = clazz through reflection. newInstance (); for (int I = 0; I <colLength; I ++) {String colName = metaData. getColumnName (I + 1); Object colValue = resultSet. getObject (colName); if (colValue = null) {colValue = "";} Field field = clazz. getDeclaredField (colName); field. setAccessible (true); field. set (resultObject, colValue);} list. add (resultObject) ;}return list ;}}

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