插入
/**
* 类名对应表，属性对应字段
* @param obj 传入的对象
* @return
*/
public static boolean insert(Object obj) {
boolean flag = false;
Class<?> c = obj.getClass(); //获取obj的Class
//利用StringBuffer进行插入SQL语句的构造
//通过反射获取类名映射表名
StringBuffer sb1 = new StringBuffer("insert into "+ c.getSimpleName() +"(");
StringBuffer sb2 = new StringBuffer(" values(");
Field[] field = c.getDeclaredFields(); //通过反射获取对象的属性数组
for(int i = 0; i < field.length; i++) { //遍历属性构造SQL语句
if(i != field.length-1) {
sb1.append(field[i].getName()).append(",");
sb2.append("?,");
}else {
sb1.append(field[i].getName()).append(")");
sb2.append("?);");
}
}
String sql = sb1.append(sb2).toString();
//获取数据库连接，进行数据库操作
Connection conn = getConnection();
PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
for(int i = 0; i < field.length; i++) {
field[i].setAccessible(true); //设置属性的可访问性，可以访问私有属性
try { //通过Field的get(Object)方法获取Object对象的属性值
ps.setObject(i+1, field[i].get(obj)); //对预编译的SQL语句中的？进行赋值
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
System.out.println(ps); //返回执行的SQL语句
flag = ps.execute(); //执行SQL
} catch (SQLException e) {
e.printStackTrace();
}finally {
close(ps);
close(conn);
}
return flag;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
2、删除
/**
* 通过主键(默认第一个属性)删除对象
* @param obj
* @return
*/
public static boolean delete(Object obj) {
boolean flag = false;
Class<?> c = obj.getClass(); //获取obj的Class
//构造删除的SQL语句
StringBuffer sb = new StringBuffer("delete from ");
sb.append(c.getSimpleName()).append(" where ");
//获取对象属性数组
Field[] field = c.getDeclaredFields();
//设置第一个属性的可访问性
field[0].setAccessible(true);
//获取第一个属性的属性名构造删除sql
sb.append(field[0].getName()).append("=?");
String sql = sb.toString();
Connection conn = getConnection();
PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
ps.setObject(1, field[0].get(obj));
System.out.println(ps);
flag = ps.execute();
} catch (SQLException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}finally {
close(ps);
close(conn);
}
return flag;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
3、修改
/**
* 模拟jdbc的更新操作，默认第一个属性为主键
* @param obj
* @return
*/
public static boolean update(Object obj) {
boolean flag = false;
Class<?> c = obj.getClass();
StringBuffer sb = new StringBuffer("update "+ c.getSimpleName() +" set ");
Field[] field = c.getDeclaredFields();
for(int i = 1; i < field.length; i++) {
if(i != field.length-1) {
sb.append(field[i].getName()).append("=?,");
}else {
sb.append(field[i].getName()).append("=? where ");
}
}
sb.append(field[0].getName() + "=?");
String sql = sb.toString();
Connection conn = getConnection();
PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
for(int i = 1; i < field.length; i++) {
field[i].setAccessible(true);
ps.setObject(i, field[i].get(obj));
}
field[0].setAccessible(true);
ps.setObject(field.length, field[0].get(obj));
System.out.println(ps);
flag = ps.execute();
} catch (SQLException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}finally {
close(ps);
close(conn);
}
return flag;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
4、查询，查询操作不需要传入一个对象，只需要一个类的Class就可以
/**
* 模拟框架，通过对象的Class获取对应表中的所有记录
* @param obj
* @return
*/
public static <T> List<T> selectAll(Class<T> c) {
String sql = "select * from "+ c.getSimpleName(); //通过反射获取类名对应表名构造SQL语句
List<T> list = new ArrayList<T>(); //存储查询结果
Field[] field = c.getDeclaredFields(); //通过反射获取所有属性
Connection conn = getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
try {
ps = conn.prepareStatement(sql);
System.out.println(ps);
rs = ps.executeQuery(); //返回结果集
while(rs.next()) {
T obj = c.newInstance(); //通过反射构造一个T类型的实例
for(int i = 0; i < field.length; i++) { //
field[i].setAccessible(true); //设置属性的可访问性(可以访问私有属性)
field[i].set(obj, rs.getObject(field[i].getName())); //通过属性名获取结果集中的值赋值到实例对象中
}
list.add(obj); //将实例对象添加到list集合
}
} catch (SQLException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace(http://www.my516.com);
}finally {
close(rs);
close(ps);
close(conn);
}
return list;
}
---------------------