自定义注解

package imooc.test;

@Table("BHL_MANAGER_USER")
public class Filter {

@Column("USER_ID")
private Integer userId;
@Column("USER_NAME")
private String userName;
@Column("USER_PWD")
private String userPwd;
@Column("USER_REALNAME")
private String userRname;

public Integer getUserId() {
return userId;
}
public void setUserId(Integer userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPwd() {
return userPwd;
}
public void setUserPwd(String userPwd) {
this.userPwd = userPwd;
}
public String getUserRname() {
return userRname;
}
public void setUserRname(String userRname) {
this.userRname = userRname;
}


}

===================

package imooc.test;


@Table("BHL_ROLE")
public class Filter2 {

@Column("ROLE_ID")
private Integer roleId;
@Column("ROLE_NAME")
private String roleName;
@Column("ORDERNO")
private String orderNo;

public Integer getRoleId() {
return roleId;
}
public void setRoleId(Integer roleId) {
this.roleId = roleId;
}
public String getRoleName() {
return roleName;
}
public void setRoleName(String roleName) {
this.roleName = roleName;
}
public String getOrderNo() {
return orderNo;
}
public void setOrderNo(String orderNo) {
this.orderNo = orderNo;
}


}

===================

package imooc.test;


import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface Table {
String value();
}

===================

package imooc.test;


import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Column {
String value();
}

===================

package imooc.test;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;


//模拟hibernate的映射
public class Test {


public static void main(String[] args) {

Filter f1 = new Filter();
f1.setUserId(7);
f1.setUserName("test5");

Filter f2 = new Filter();
f2.setUserName("bhl_test");

Filter f3 = new Filter();
f3.setUserRname("bhl,test1,test2");


String sql1 = query(f1);
System.out.println(sql1);
executeQuery(sql1,1);
System.out.println();

String sql2 = query(f2);
System.out.println(sql2);
executeQuery(sql2,1);
System.out.println();

String sql3 = query(f3);
System.out.println(sql3);
executeQuery(sql3,1);
System.out.println();

Filter2 f4 = new Filter2();
f4.setRoleName("档案管理员");
String sq4 = query(f4);
System.out.println(sq4);
executeQuery(sq4,2);

}

private static void executeQuery(String sql,int type) {
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.1.9:1521:orcl", "bcloud", "bcloud");
PreparedStatement findPst = conn.prepareStatement(sql);
ResultSet rs = findPst.executeQuery();
while (rs.next()) {
if (type==1) {
int userId = rs.getInt(1);
String userName = rs.getString(2);
String userPwd = rs.getString(3);
String realName = rs.getString(4);
System.out.println("userId:"+userId+" userName:"+userName+" userPwd:"+userPwd+" realName:"+realName);
}else {
int roleId = rs.getInt(1);
String roleName = rs.getString(2);
int orderNo = rs.getInt(3);
System.out.println("roleId:"+roleId+" roleName:"+roleName+"  orderNo:"+orderNo);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}


//最终目的建立属性到数据库表字段的映射,拼装sql语句
public static String query(Object f){

StringBuilder sb = new StringBuilder();

//1.获取到class

Class c = f.getClass();

//2.获取到Table名字

boolean exists =  c.isAnnotationPresent(Table.class);
if (!exists) {
return null;
}
Table t = (Table) c.getAnnotation(Table.class);
String tableName =  t.value();
sb.append("select * from ").append(tableName).append(" where 1=1 ");

//3.遍历所有字段

Field[] farray = c.getDeclaredFields();
for (Field field : farray) {

//4.处理每个字段对应的sql

//4.1 拿到字段名(属性对应数据库表中的字段,即注解的值)
//4.2 拿到字段值(数据库表中的)
//4.3 拼装sql
boolean fexist = field.isAnnotationPresent(Column.class);
if (!fexist) {
continue;

}

Column column = field.getAnnotation(Column.class);//获得注解对象

String columnName = column.value();//获得注解对象的值

//取得属性的get方法
String fieldName = field.getName();
String getMethodName = "get"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1); 

//filedValue类型不唯一,所以定义成Object
Object fieldValue = null;
try {
Method getMethod = c.getMethod(getMethodName);
fieldValue = getMethod.invoke(f);

} catch (Exception e) {
e.printStackTrace();
}
//拼装sql,如果fieldValue是null或者是Integer类型且值为0时
if (fieldValue==null||(fieldValue instanceof Integer && (Integer)fieldValue==0)) {
continue;
}
sb.append(" and ").append(columnName);
if (fieldValue instanceof String) {
if (((String) fieldValue).contains(",")) {
sb.append(" in(");
String[] values = ((String) fieldValue).split(",");
for (String v : values) {
sb.append("'").append(v).append("'").append(",");
}
sb.deleteCharAt(sb.length()-1).append(")");//将最末尾的,删掉
}else {
sb.append(" = ").append("'").append(fieldValue).append("'");
}
}else {
sb.append(" = ").append(fieldValue);
}

}
return sb.toString();
}


}