一、JDBC1.0版本BaseDao工具类
JDBC1.0API + 元数据 + BeanUtils组件
二、JDBC2.0版本BaseDao工具类
DbUtils组件
三、自定义BaseDao工具类(3.0 版本)
表的字段名称和实体名称一定一致。
使用技术:
反射技术+泛型反射技术 + DbUtils组件
切记:
1.泛型反射技术主要用于获取参数化类型对象,即泛型的字节码对象(t.class)
原因:我们自定义basedao工具类,不把查询实体的字节码对象传入,而是已
泛型的方式来传入。所以我们需要泛型的反射,来获取泛型的字节码
对象,从而做到通用组件。
2.
使用反射技术获取表名、字段,来自定义BaseDao工具类。
【此时表名和实体名要一致;表的字段名要和实体的属性名要一致。】
sql脚本
SHOW CREATE TABLE member;CREATE TABLE `member` (
`id` VARCHAR(200) NOT NULL,
`name` VARCHAR(20) NOT NULL,
`password` VARCHAR(20) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8
JdbcUtils.java
public class JdbcUtils {
private static ComboPooledDataSource dataSource;
static {
dataSource=new ComboPooledDataSource();
}
public static QueryRunner getQr() {
QueryRunner qr=new QueryRunner(dataSource);
return qr;
}
}
BaseDao.java
public class BaseDao<T> {
private Class t;
private String tableName;
public BaseDao() {
Type type = this.getClass().getGenericSuperclass();
ParameterizedType pa=(ParameterizedType) type;
Type[] types = pa.getActualTypeArguments();
Class clazz=(Class) types[0];
t=clazz;
tableName=t.getSimpleName();
}
public List<T> findById(String id) throws SQLException {
String sql="select * from "+tableName+" where id =?";
QueryRunner qr = JdbcUtils.getQr();
return qr.query(sql, new BeanListHandler<T>(t), id);
}
public List<T> selectAll() throws SQLException {
String sql="select * from "+tableName ;
QueryRunner qr = JdbcUtils.getQr();
return qr.query(sql, new BeanListHandler<T>(t));
}
}
Member
public class Member {
private String id ;
private String name;
private String password;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
MemberDao
public class MemberDao extends BaseDao<Member> {
}
App.java
public class App {
public static void main(String[] args) throws SQLException {
MemberDao dao=new MemberDao();
List<Member> result = dao.selectAll();
System.out.println(result);
}
}
c3p0-config.xml
<c3p0-config>
<!-- 默认数据库 -->
<default-config>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/day11</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="initialPoolSize">3</property>
<property name="maxPoolSize">6</property>
<property name="maxIdleTime">1000</property>
</default-config>
<!-- 可以使用多数据源
<named-config name="db2">
<property name="jdbcUrl">jdbc:mysql://localhost:3306/test</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="initialPoolSize">3</property>
<property name="maxPoolSize">6</property>
<property name="maxIdleTime">1000</property>
</named-config>
-->
</c3p0-config>
四、自定义BaseDao工具类(4.0 版本)
表的字段名称和实体名称可以不一致。
使用技术:
注解+反射技术+泛型反射技术 + DbUtils组件
切记:
1.泛型反射技术主要用于获取参数化类型对象,即泛型的字节码对象(t.class)
原因:我们自定义basedao工具类,不把查询实体的字节码对象传入,而是已
泛型的方式来传入。所以我们需要泛型的反射,来获取泛型的字节码
对象,从而做到通用组件。
2.
使用反射技术获取表名、字段,来自定义BaseDao工具类。
【此时表名和实体名要一致;表的字段名要和实体的属性名要一致。】
4.1 sql脚本
CREATE TABLE `admin` (
`id` varchar(100) NOT NULL,
`username` varchar(20) DEFAULT NULL,
`pwd` varchar(20) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
4.2 注解
Column.java
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Column {
String value();
}
id.java
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface id {
String value() default "";
}
Table.java
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Table {
String value();
}
4.3 数据连接层
JdbcUtils.java
public class JdbcUtils {
private static ComboPooledDataSource dataSource;
static {
dataSource=new ComboPooledDataSource();
}
public static QueryRunner getQr() {
QueryRunner qr=new QueryRunner(dataSource);
return qr;
}
}
c3p0-config.xml
<c3p0-config>
<!-- 默认数据库 -->
<default-config>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/day11</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="initialPoolSize">3</property>
<property name="maxPoolSize">6</property>
<property name="maxIdleTime">1000</property>
</default-config>
<!-- 可以使用多数据源
<named-config name="db2">
<property name="jdbcUrl">jdbc:mysql://localhost:3306/test</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="initialPoolSize">3</property>
<property name="maxPoolSize">6</property>
<property name="maxIdleTime">1000</property>
</named-config>
-->
</c3p0-config>
4.4 数据操作层
BaseDao.java
public class BaseDao<T> {
private Class<T> clazz;
private String tableName;
private String id_primary;
public BaseDao(){
Type type = this.getClass().getGenericSuperclass();
ParameterizedType pt = (ParameterizedType) type;
Type[] types = pt.getActualTypeArguments();
clazz = (Class<T>) types[0];
Table table = clazz.getAnnotation(Table.class);
tableName = table.value();
Field[] fs = clazz.getDeclaredFields();
for (Field f : fs) {
f.setAccessible(true);
id anno_id = f.getAnnotation(id.class);
if (anno_id != null) {
Column column = f.getAnnotation(Column.class);
id_primary = column.value();
break;
}
}
System.out.println("表:" + tableName);
System.out.println("主键:" + id_primary);
}
public T findById(int id){
try {
String sql = "select * from " + tableName + " where " + id_primary +"=?";
return JdbcUtils.getQr().query(sql, new BeanHandler<T>(clazz), id);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public List<T> getAll(){
try {
String sql = "select * from " + tableName;
return JdbcUtils.getQr().query(sql, new BeanListHandler<T>(clazz));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
class BeanHandler<T> implements ResultSetHandler<T>{
private Class<T> clazz;
public BeanHandler(Class<T> clazz) {
this.clazz = clazz;
}
@Override
public T handle(ResultSet rs) throws SQLException {
try {
T t = clazz.newInstance();
if (rs.next()) {
Field[] fs = clazz.getDeclaredFields();
for (Field f : fs) {
String fieldName = f.getName();
Column column = f.getAnnotation(Column.class);
String columnName = column.value();
Object columnValue = rs.getObject(columnName);
BeanUtils.copyProperty(t, fieldName, columnValue);
}
}
return t;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
class BeanListHandler<T> implements ResultSetHandler<List<T>>{
private Class<T> clazz;
public BeanListHandler(Class<T> clazz){
this.clazz = clazz;
}
@Override
public List<T> handle(ResultSet rs) throws SQLException {
List<T> list = new ArrayList<T>();
try {
while (rs.next()) {
T t = clazz.newInstance();
Field[] fs = clazz.getDeclaredFields();
for (Field f : fs) {
String fieldName = f.getName();
Column column = f.getAnnotation(Column.class);
String columnName = column.value();
Object columnValue = rs.getObject(columnName);
BeanUtils.copyProperty(t, fieldName, columnValue);
}
list.add(t);
}
return list;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
4.5 使用
Member
@Table("admin")
public class Member {
@Column("id")
private String id ;
@Column("username")
private String name;
@Column("pwd")
private String password;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
MemberDao
public class MemberDao extends BaseDao<Member> {
}
App.java
public class App {
public static void main(String[] args) throws SQLException {
MemberDao dao=new MemberDao();
List<Member> selectAll = dao.getAll();
System.out.println(selectAll);
}
}