JavaWeb 后端 <十一> 之 DBUtils 框架 （基本使用 结果集 事务处理 对表读取）
一、数据库操作框架
1、ORM：Object Relation Mapping
Hibernate：非常流行
JPA：Java Persistent API.ORM标准
MyBatis：2010年开始。之前叫做iBatis（重视）
2、JDBC封装框架
DBUtils
Spring JDBC Template
二、Apache的DBUtils框架（会用：练习作业）
1、基本的使用
DBCPutil
public class DBCPUtil {
private static DataSource dataSource;
static{
try {
InputStream in = DBCPUtil.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
Properties props = new Properties();
props.load(in);
dataSource = BasicDataSourceFactory.createDataSource(props);
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}
public static DataSource getDataSource(){
return dataSource;
}
public static Connection getConnection(){
try {
return dataSource.getConnection();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
dbcpconfig.properties 配置文件 对dbcp进行配置
QueryRunner 的使用 CRUD
/*
create database day18;
use day18;
create table student(
id int primary key,
name varchar(100),
birthday date
);
*/
public class DBUtilCRUD {
private QueryRunner qr = new QueryRunner(DBCPUtil.getDataSource());
@Test
public void testAdd() throws SQLException{
qr.update("insert into student values(?,?,?)", 1,"杨洋",new Date());
}
@Test
public void testUpdate() throws SQLException{
qr.update("update student set birthday=? where id=?", "1993-08-01",1);
}
@Test
public void testDel() throws SQLException{
qr.update("delete from student where id=?", 1);
}
//批处理插入10条
@Test
public void testBatch() throws SQLException{
Object params[][] = new Object[10][];//高维：记录的条数。低维：每条记录需要的参数
for(int i=0;i<params.length;i++){
params[i] = new Object[]{i+1,"杨洋"+(i+1),new Date()};
}
qr.batch("insert into student values(?,?,?)", params);
}
//大文本：了解
/*
create table t1(
id int primary key,
content longtext
);
*/
@Test//大文本类型===Clob
public void testClob()throws Exception{
File file = new File("src/pqy&sx.txt");//文件很大，内存浪费
Reader reader = new FileReader(file);
char ch[] = new char[(int)file.length()];
reader.read(ch);
reader.close();
Clob clob = new SerialClob(ch);
qr.update("insert into t1 values(?,?)", 1,clob);//类型不批配。流不是数据库的类型
}
//大二进制：了解
/*
create table t2(
id int primary key,
content longblob
);
*/
@Test//大二进制类型===Blob
public void testBlob()throws Exception{
InputStream in = new FileInputStream("src/22.jpg");
byte b[] = new byte[in.available()];
in.read(b);
in.close();
Blob blob = new SerialBlob(b);
qr.update("insert into t2 values(?,?)", 1,blob);//类型不批配。流不是数据库的类型
}
}
2、各种结果处理器的使用 ResultSetHandler
public class ResultSetHandlerDemo {
private QueryRunner qr = new QueryRunner(DBCPUtil.getDataSource());
//ArrayHandler:适合结果只有一条的情况。把第一条记录的每列的值封装到一个Object[]数组中
@Test
public void test1() throws Exception{
Object[] objs = qr.query("select * from student", new ArrayHandler());
for(Object obj:objs)
System.out.println(obj);
}
//ArrayListHandler:适合结果有多条的情况。把每列的值封装到Object[]数组中，把Object[]放到List中
@Test
public void test2() throws Exception{
List<Object[]> list = qr.query("select * from student", new ArrayListHandler());
for(Object[] objs:list){
System.out.println("----------------");
for(Object obj:objs){
System.out.println(obj);
}
}
}
//ColumnListHandler:适合取某列的值。把取到值封装到List中
@Test
public void test3() throws Exception{
List<Object> list = qr.query("select * from student", new ColumnListHandler("name"));
for(Object obj:list){
System.out.println(obj);
}
}
//KeyedHandler:查询多条记录。每条记录封装到一个Map中，key：字段名，value：字段值。再把Map作为value放到另外一个Map中，该Map的key为指定的列值作为key。
@Test
public void test4() throws Exception{
Map<Object,Map<String,Object>> bmap = qr.query("select * from student", new KeyedHandler("id"));
for(Map.Entry<Object,Map<String,Object>> bme:bmap.entrySet()){
System.out.println("--------------------");
for(Map.Entry<String, Object> lme:bme.getValue().entrySet()){
System.out.println(lme.getKey()+"="+lme.getValue());
}
}
}
//MapHandler:适合一条结果。封装到一个Map中，key：字段名，value：字段值
@Test
public void test5() throws Exception{
Map<String,Object> map = qr.query("select * from student", new MapHandler());
for(Map.Entry<String, Object> lme:map.entrySet()){
System.out.println(lme.getKey()+"="+lme.getValue());
}
}
//MapListHandler:适合多条结果。把每条封装到一个Map中，key：字段名，value：字段值，在把Map封装到List中
@Test
public void test6() throws Exception{
List<Map<String,Object>> list = qr.query("select * from student", new MapListHandler());
for(Map<String,Object> map:list){
System.out.println("--------------------");
for(Map.Entry<String, Object> lme:map.entrySet()){
System.out.println(lme.getKey()+"="+lme.getValue());
}
}
}
//ScalarHandler:适合取结果只有一行和一列的情况。
@Test
public void test7() throws Exception{
Object obj = qr.query("select count(*) from student", new ScalarHandler(1));
// System.out.println(obj.getClass().getName());
Long l = (Long)obj;
System.out.println(l.intValue());
System.out.println(obj);
}
}
三、实际开发中事务如何管理(非常好)
对事务的控制
1、写4个版本的代码：AOP
1.0
public interface AccountDao {
/**
* 转账
* @param sourceAccountName 转出账户
* @param targetAccontName 转入账户
* @param money 交易金额
*/
void transfer(String sourceAccountName,String targetAccontName,float money);
}
/*
create table account(
id int primary key auto_increment,
name varchar(40),
money float
)character set utf8 collate utf8_general_ci;
insert into account(name,money) values('aaa',1000);
insert into account(name,money) values('bbb',1000);
insert into account(name,money) values('ccc',1000);
*/
public class AccountDaoImpl implements AccountDao {
private QueryRunner qr = new QueryRunner();
public void transfer(String sourceAccountName, String targetAccontName,
float money) {
Connection conn = null;
try {
conn = DBCPUtil.getConnection();
conn.setAutoCommit(false);//开启事务
qr.update(conn,"update account set money=money-? where name=?", money,sourceAccountName);
// int i=1/0;
qr.update(conn,"update account set money=money+? where name=?", money,targetAccontName);
} catch (Exception e) {
if(conn!=null){
try {
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
e.printStackTrace();
}finally{
if(conn!=null){
try {
conn.commit();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
public interface BusinessService {
/**
* 转账
* @param sourceAccountName 转出账户
* @param targetAccontName 转入账户
* @param money 交易金额
*/
void transfer(String sourceAccountName,String targetAccontName,float money);
}
public class BusinessServiceImpl implements BusinessService {
private AccountDao dao = new AccountDaoImpl();
public void transfer(String sourceAccountName, String targetAccontName,
float money) {
dao.transfer(sourceAccountName, targetAccontName, money);
}
}
public class Client {
public static void main(String[] args) {
BusinessService s = new BusinessServiceImpl();
s.transfer("aaa", "bbb", 100);
}
}
2.0
//DAO层：不能牵扯到任何业务有关的逻辑。
//DAO:只负责CRUD
public interface AccountDao {
/**
* 根据户名查询账户
* @param accountName
* @return
*/
Account findByName(String accountName);
/**
* 更新账户
* @param account
*/
void updateAcount(Account account);
}
public class AccountDaoImpl implements AccountDao {
private QueryRunner qr = new QueryRunner();
private Connection conn;
public AccountDaoImpl(Connection conn){
this.conn = conn;
}
public Account findByName(String accountName) {
try {
return qr.query(conn,"select * from account where name=?", new BeanHandler<Account>(Account.class),accountName);
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public void updateAcount(Account account) {
try {
qr.update(conn,"update account set money=? where id=?", account.getMoney(),account.getId());
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
public class Account {
private int id;
private String name;
private float money;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getMoney() {
return money;
}
public void setMoney(float money) {
this.money = money;
}
}
public interface BusinessService {
/**
* 转账
* @param sourceAccountName 转出账户
* @param targetAccontName 转入账户
* @param money 交易金额
*/
void transfer(String sourceAccountName,String targetAccontName,float money);
}
//业务层控制事务
public class BusinessServiceImpl implements BusinessService {
public void transfer(String sourceAccountName, String targetAccontName,
float money) {
Connection conn = null;
try {
conn = DBCPUtil.getConnection();
conn.setAutoCommit(false);
AccountDao dao = new AccountDaoImpl(conn);
Account sAccount = dao.findByName(sourceAccountName);
Account tAccount = dao.findByName(targetAccontName);
sAccount.setMoney(sAccount.getMoney() - money);
tAccount.setMoney(tAccount.getMoney() + money);
dao.updateAcount(sAccount);
// int i=1/0;
dao.updateAcount(tAccount);
} catch (Exception e) {
if (conn != null) {
try {
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
e.printStackTrace();
} finally {
if (conn != null) {
try {
conn.commit();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
public class Client {
public static void main(String[] args) {
BusinessService s = new BusinessServiceImpl();
s.transfer("aaa", "bbb", 100);
}
}
3.0
//封装了所有与事务有关的方法
public class TransactionManager {
private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
public static Connection getConnection(){
Connection conn = tl.get();
if(conn==null){//从当前线程中获取链接
conn = DBCPUtil.getConnection();
tl.set(conn);
}
return conn;
}
public static void startTransaction(){
try {
Connection conn = getConnection();
conn.setAutoCommit(false);
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void rollback(){
try {
Connection conn = getConnection();
conn.rollback();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void commit(){
try {
Connection conn = getConnection();
conn.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void release(){
try {
Connection conn = getConnection();
conn.close();
tl.remove();//从当前线程中解绑。 与服务器实现有关：服务器采用线程池。
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//业务层控制事务
public class BusinessServiceImpl implements BusinessService {
private AccountDao dao = new AccountDaoImpl();
public void transfer(String sourceAccountName, String targetAccontName,
float money) {
try {
TransactionManager.startTransaction();
Account sAccount = dao.findByName(sourceAccountName);
Account tAccount = dao.findByName(targetAccontName);
sAccount.setMoney(sAccount.getMoney() - money);
tAccount.setMoney(tAccount.getMoney() + money);
dao.updateAcount(sAccount);
int i=1/0;
dao.updateAcount(tAccount);
} catch (Exception e) {
TransactionManager.rollback();
e.printStackTrace();
} finally {
TransactionManager.commit();
TransactionManager.release();
}
}
}
public class AccountDaoImpl implements AccountDao {
private QueryRunner qr = new QueryRunner();
public Account findByName(String accountName) {
try {
return qr.query(TransactionManager.getConnection(),"select * from account where name=?", new BeanHandler<Account>(Account.class),accountName);
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public void updateAcount(Account account) {
try {
qr.update(TransactionManager.getConnection(),"update account set money=? where id=?", account.getMoney(),account.getId());
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
4.0 AOP（面向切面编程）
//AOP
public class BeanFactory {
public static BusinessService getBusinessService(){
final BusinessService s = new BusinessServiceImpl();
BusinessService proxyS = (BusinessService)Proxy.newProxyInstance(s.getClass().getClassLoader(),
s.getClass().getInterfaces(),
new InvocationHandler() {
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
try {
TransactionManager.startTransaction();
Object rtValue = method.invoke(s, args);
return rtValue;
} catch (Exception e) {
TransactionManager.rollback();
throw new RuntimeException(e);
} finally {
TransactionManager.commit();
TransactionManager.release();
}
}
});
return proxyS;
}
}
2、ThreadLocal（很重要）
//特点：一个线程存的东西，只有该线程才能取出来。线程局部变量。
//模拟
public class ThreadLocal{
//类似Map的结构
private Map<Runnable,Object> map = new HashMap<Runnable,Object>();
public void set(Object obj){
map.put(Thread.currentThread(),obj);
}
public void remove(){
map.remove(Thread.currentThread());
}
public Object get(){
map.get(Thread.currentThread());
}
}
四、利用DBUtils框架进行多表的读取
1、一对多
2、多对多
3、一对一