数据篇之JDBC连接MySQL

ps: 前段时间做了一个不存在网络，获取设备存储到mysql中的数据，然后根据数据生成二维码，用户通过扫描二维码进行操作的android 程序。

其中一个需求：在没有网络的情况，要读取mysql中的数据，然后进行增删查改

解决方式：1.采用java中的jdbc链接mysql，然后进行增删查改

准备工作：mysql-connector-java-xxx-bin.jar是不可少的



（一）存储连接mysql的账号和密码，采用properties来保存，将properties文件放置到assets文件夹下

//获取Properties
public Properties getProperties() {
InputStream inputStream = null;
try {
properties = new Properties();
inputStream = BaseApplication.getContext().getAssets().open(path);
properties.load(inputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (inputStream != null) {
inputStream.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return properties;
}

（二）加载jdbc驱动，连接mysql:

Connection接口常用api：
1.prepareStatement()：创建一个PrepareStatement对象，用于操作数据库
2.setAutoCommit():设置是否自动提交，与事务有关
3.rollback():回滚事务
4.setSavePoint():设置一个恢复点，与事务有关
5.close():关闭数据库
6.commit():提交操作，与事务有关

//驱动名
public static final String DBDRIVER = "org.gjt.mm.mysql.Driver";
private java.sql.Connection connection;
//MySQL地址
public static final String DBURL = "jdbc:mysql://192.168.0.xx:3306/yjqwxmp?useUnicode=true&characterEncoding=utf8";

public void connnetJDBC() {
try {
// 加载jdbc驱动
Class.forName(DBDRIVER);
//通过url,和账号密码，链接mysql,获取connection
connection = DriverManager.getConnection(DBURL, getProperties());
//注意点：用到了事务，所以取消自动提交，反之，省略
connection.setAutoCommit(false);
} catch (Exception e) {
e.printStackTrace();
} finally {

}
}

（三）通过PreparedStatement（预处理）接口操作数据库：

PreparedStatement是Statement的子类，效率更高。

PreparedStatement的使用原理：
采用"?"的占位符，然后根据"?"扥顺序来设置内容

除了Statement的属性外，还新增属性：
1. int executeUpdate():执行设置的预处理sql语句
2. resultSet executeQuery():执行数据库的查询操作，返回resultSet
3. void   setint(int parameterIndex,int  x):根据指定索引，设置整形数据
除此之外，还有setFloat(),setString(),setDate()，根据指定索引，设置各种类型数据

注意点：setDate()这个方法参数是java.sql.Date,
若是java.util.Date需要通过getTime()转换为java.sql.Date

查询案例：
//查询的sql
public static final String GASWORKER_SELECT_SQL = "select id, gas_worker_id from t_gasworker_msg where gas_worker_id = ?";
//包含数据的结果集
ResultSet resultSet = null;
//执行增删查改sql的接口
PreparedStatement statement = null;

statement = connection.prepareStatement(GASWORKER_SELECT_SQL);
//"?"的索引为1，根据索引来设置 gas_worker_id = a123
statement.setString(1,"a123");
resultSet = statement.executeQuery();
while(resultSet.next()){
//ResultSet中的所有数据都可以通过getString()方法获得
String id = resultSet.getString("id");
}
statement.close(); //关闭PreparedStatement
result.close();    //关闭结果集
connection.close();//关闭连接的接口

（四）使用事务批量处理sql:

事务：所有操作要门一起成功，要门一起失败
MySQL中事务处理顺序：
1. 取消自动提交：connection.setAutoCommint(false)将执行操作先存放在 session
(每个链接数据库的用户都是 session)
2.开启事务
3.编写增，删，查，改sql语句
4.提交事务:connection.commit();
5.事务回滚：若是执行sql发生错误，取消操作，或者回滚到指定的记录点上

批量插入数据到数据库的案例：
//首先设置，自动提交取消
connection.setAutoCommit(false);

public static final String GASFILTRATIONRECODER_INSERT = "insert into t_gas_filtration_recoder (gas_exchange_index,staff_ic_id) values (?,?)";
PreparedStatement insert_Statement = null;

try{
insert_Statement  =connection.prepareStatement(GASFILTRATIONRECODER_INSERT);
for(int i=0；i<2;++i){
insert_Statement.setString(1,String.valuesOf(i));
insert_Statement.setString(2,"a"+i);
insert_Statement.addBatch();//添加事务
}

//批量执行
int[]  i= statement.executeBatch();
//事务提交
connection.commit();
if(i==2){  //当执行sql的数量为添加事务的总数时，执行成功

}
}catch(Exception e){
try {
//若是事务执行sql错误，回滚事务
connection.rollback();
} catch (Exception e2) {
}
e.printStackTrace();

}finally{
if (insert_Statement != null) {
insert_Statement.close();
}
if (connection != null) {
connection.close();
connection = null;
}

}

(五)使用元数据分析数据库：

ResultSetMetaData:获取到Resultet对象中列的数据类型和属性信息得对象
1.int getColumnnCount():获取一个查询结果中的列数
2.boolean isAutolncrement(int column):判断指定列是否为自动编号
3.string getColumnName(int column):返回指定列的名字

个人指定需求案例：

项目需求：
1.在mysql中查询到新数据，修改新数据标示，将新数据保存到本地
（android 自带数据库 SQLiteDatabase）
2.向myslq中插入数据，更新数据，删除数据，mysql数据库和SQLiteDatabase同步
3.合并多条数据为一条数据，插入MySql中

将jdbc操作封装在一个utls类中：

public class JDBCUtils {
public static final String DBDRIVER = "org.gjt.mm.mysql.Driver";
private static final String path = "gasstation.properties";
private java.sql.Connection connection;
private Properties properties;
//数据库的url
public static final String DBURL = "jdbc:mysql://192.168.0.xx:3306/yjqwxmp?useUnicode=true&characterEncoding=utf8";

private String selectSql1 = "select  geid, gas_station_gun_id,gas_type,gas_volume,gas_desity,staff_ic_id,consumer_ic_id,group_no,gas_exchange_index,gas_exchange_time_start,gas_exchange_time_end  from t_gas_exchange_info  where upload_flg = 0  and ";

public String workNumber = "staff_ic_id =";

public static final String GASMSG_UPDATE_SQL = "update t_gas_msg  set gas_machine_id=? where gas_station = ? ";

public static final String GASMSG_SELECT_SQL = "select id ,gas_station,gas_machine_id from t_gas_msg where gas_station = ?";

public static final String GASWORKER_INSERT_SQL = "insert into t_gasworker_msg(gas_worker_id) values(?)";

public static final String GASWORKER_UPDATE_SQL = "update t_gasworker_msg set gas_worker_id=? where gas_worker_id =?";
public static final String GASFILTRATIONRECODER_INSERT = "insert into t_gas_filtration_recoder (gas_exchange_index,staff_ic_id,gas_type,gas_volume,gas_exchange_time_end,merge_flg,data_source) values (?,?,?,?,?,?,?)";

public static final String GASFILITRATIONRECODER_UPDATE = "update t_gas_filtration_recoder set merge_flg =1 where gas_exchange_index=";

public static final String AND = " and geid=";

public JDBCUtils() {
connnetJDBC();
}

public void connnetJDBC() {
try {
// 加载jdbc驱动
Class.forName(DBDRIVER);
connection = DriverManager.getConnection(DBURL, getProperties());
connection.setAutoCommit(false);// 取消自动提交
} catch (Exception e) {
e.printStackTrace();
} finally {
LogController.i("result_return", connection + " ");
}
}
//关闭连接
public void closeConnection() {
try {
if (connection != null) {
connection.close();
connection = null;
}
} catch (Exception e) {
}

}
//获取Properties
public Properties getProperties() {
InputStream inputStream = null;
try {
properties = new Properties();
inputStream = BaseApplication.getContext().getAssets().open(path);
properties.load(inputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (inputStream != null) {
inputStream.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return properties;
}

//获取到android本地数据库上的员工信息
public List<String> getGasWorkerRecoder() {
Cursor cursor = null;
try {
ContentResolver resolver = BaseApplication.getContext()
.getContentResolver();
cursor = resolver.query(DateProviderContract.GASWORKER_URI, null,
null, null, null);
if (cursor.moveToFirst()) {
List<String> list = new ArrayList<String>();
do {
list.add(cursor.getString(cursor
.getColumnIndex(DateProviderContract.COLUMN_NUMBER)));
} while (cursor.moveToNext());
return list;
}
} catch (Exception e) {
} finally {
try {
if (cursor != null) {
cursor.close();
}
} catch (Exception e2) {
}
}
return null;
}

//获取mySql中最新设备信息，且修改新信息得标志为旧信息，将获取到的信息存到本地
public void operateGasRecoder() {
ResultSet resultSet = null;
PreparedStatement statement = null, insert_Statement = null;
List<ContentValues> list = null;
List<String> workerList = getGasWorkerRecoder();
if (workerList == null) {
closeConnection();
return;
}
LogController.i("tiemss", "connection " + connection);
try {
if (connection == null) {
return;
}
LogController.i("tiemss", "list size" + workerList.size());
StringBuffer buffer = new StringBuffer();
buffer.append(selectSql1);
for (int i = 0; i < workerList.size(); i++) {
if (i != 0) {
buffer.append(" or ");
} else {
if (workerList.size() > 1) {
buffer.append("(");
}
}
buffer.append(workNumber);
buffer.append("'");
buffer.append(workerList.get(i).trim());
buffer.append("'");
if (i == workerList.size() - 1) {
if (workerList.size() > 1) {
buffer.append(")");
}
}
}
statement = connection.prepareStatement(buffer.toString());

resultSet = statement.executeQuery();
insert_Statement = connection
.prepareStatement(GASFILTRATIONRECODER_INSERT);
StringBuffer buffer2 = null;
while (resultSet.next()) {
if (list == null) {
list = new ArrayList<ContentValues>();
buffer2 = new StringBuffer();
buffer2.append("update t_gas_exchange_info set  upload_flg = 1 where geid = ");
}
buffer2.append(resultSet.getInt(1));
buffer2.append(AND);
insertGasFiltrayionTable(resultSet, insert_Statement);
list.add(getContentValues(resultSet));
}
if (buffer2 != null) {
String str = buffer2.toString().trim();
LogController.i("tiemss", str
.substring(0, str.lastIndexOf(AND)).trim());
insert_Statement.addBatch(str
.substring(0, str.lastIndexOf(AND)).trim());
}
int[] insertSize = insert_Statement.executeBatch();
connection.commit();
// 保存到本地 android 数据库，
if (insertSize.length > 0) {
ContentValues[] values = new ContentValues[list.size()];
for (int i = 0; i < list.size(); i++) {
values[i] = list.get(i);
}
ContentResolver resolver = BaseApplication.getContext()
.getContentResolver();
//批量插入
int length = resolver.bulkInsert(
DateProviderContract.RECODER_URI, values);
LogController.i("result_return", length + " ");
}
} catch (Exception e) {
e.printStackTrace();
if (resultSet != null) {
try {
connection.rollback();// 事务回滚
} catch (Exception e2) {
}
}
} finally {
try {

if (resultSet != null) {
resultSet.close();
}
if (statement != null) {
statement.close();
}
if (insert_Statement != null) {
insert_Statement.close();

}
if (list != null) {
list.clear();
list = null;
}
if (workerList != null) {
workerList.clear();
workerList = null;
}
closeConnection();

} catch (Exception e2) {
e2.printStackTrace();
}

}
}

//插入过滤后的数据
public void insertGasFiltrayionTable(ResultSet resultSet,
PreparedStatement statement) {
try {
statement.setInt(1, resultSet.getInt(9));
statement.setString(2, resultSet.getString(6));
statement.setInt(3, resultSet.getInt(3));
statement.setString(4, resultSet.getString(4));
statement.setTimestamp(5, resultSet.getTimestamp(11));
statement.setInt(6, 0);
statement.setString(7, null);
statement.addBatch();
} catch (Exception e) {
e.printStackTrace();
}

}

public ContentValues getContentValues(ResultSet resultSet) {
ContentValues values = new ContentValues();
try {
values.put(DateProviderContract.COLUMN_CHANGNUMBER,
resultSet.getString(9));
values.put(DateProviderContract.COLUMN_GASNUMBER,
resultSet.getString(2));
values.put(DateProviderContract.COLUMN_GASSTYLE,
resultSet.getString(3));
values.put(DateProviderContract.COLUMN_GASVOLUME,
resultSet.getString(4));
values.put(DateProviderContract.COLUMN_TIME,
resultSet.getString(11));
} catch (Exception e) {
e.printStackTrace();
}
return values;
}

//更新特殊条件过滤后的信息记录
public void upDateFiltrationRecoder(String  gaschangindex,String staff_id,String gas_type,Double gas_volume,String gas_time,String  source,String updateSql) {
if (connection == null) {
return;

}
PreparedStatement statement = null;
try {
statement = connection
.prepareStatement(GASFILTRATIONRECODER_INSERT);
statement.setInt(1, Integer.valueOf(gaschangindex));
statement.setString(2, staff_id);
statement.setInt(3, Integer.valueOf(gas_type));
statement.setString(4, String.valueOf(gas_volume));
statement.setTimestamp(5, Timestamp.valueOf(gas_time));
statement.setInt(6, 1);
statement.setString(7, source);
statement.addBatch();
statement.addBatch(updateSql);
statement.executeBatch();
connection.commit();
} catch (Exception e) {
try {
connection.rollback();
} catch (Exception e2) {
}
e.printStackTrace();
} finally {
try {
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (Exception e2) {
}

}

}

public void updateDb(int geid, Statement statement) {
StringBuilder builder = new StringBuilder();
builder.append("update t_gas_exchange_info set  upload_flg = 1 where geid =");
builder.append(geid);
try {
statement.addBatch(builder.toString());
} catch (Exception e) {
}
}

//插入设备信息到mysql中
public synchronized void operateGasSystem(SparseArray<String> array) {
if (connection == null) {
return;
}
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
statement = connection.prepareStatement(GASMSG_SELECT_SQL);
statement.setString(1, array.get(0));
resultSet = statement.executeQuery();

if (!resultSet.next()) {
statement = connection.prepareStatement(GASMSG_INSET_SQL);
statement.setString(1, array.get(0));
statement.setString(2, array.get(1).trim());
statement.execute();
connection.commit();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (statement != null) {
statement.close();
}
if (resultSet != null) {
resultSet.close();
}
closeConnection();
} catch (Exception e2) {
}

}
}

//插入员工信息到mysql中
public synchronized void operateGasWorker(SparseArray<String> array) {
if (connection == null) {
return;
}
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
statement = connection.prepareStatement(GASWORKER_SELECT_SQL);
statement.setString(1, array.get(0));
resultSet = statement.executeQuery();

if (!resultSet.next()) {
statement = connection.prepareStatement(GASWORKER_INSERT_SQL);
statement.setString(1, array.get(0));
statement.execute();
connection.commit();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (statement != null) {
statement.close();
}
if (resultSet != null) {
resultSet.close();
}
closeConnection();
} catch (Exception e2) {
}

}

}

}