利用注解动态生成sql

来源：互联网发布：修道入门知乎编辑：程序博客网时间：2024/05/21 20:24

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface DBTable {public String name() default "mytable";}

@SuppressWarnings("all")@DBTable(name="mytable")public class Person implements Serializable {@SQLInteger(constraints=@Constraints(primaryKey=true,unique=true))private int id;@SQLString(value=12)private String name;@SQLInteger(value = 5) private int age;}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface SQLInteger {

String name() default  "";
int value() default 0;
Constraints constraints() default @Constraints;



}
@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)@SuppressWarnings("all")public @interface SQLString {String name() default "";int value() default 0;Constraints constraints() default @Constraints;}
@DBTable@SuppressWarnings("all")public class Student implements Serializable{@SQLString(value=12) String name;@SQLInteger (value = 5) int age;}
@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface Constraints {boolean primaryKey() default false;boolean unique() default false;boolean NULL() default false;}
@SuppressWarnings("all")public class AnnotationParse {public static void main(String[] args) throws ClassNotFoundException {String colunm = null;Scanner sc = new Scanner(System.in);String className = sc.nextLine();Class<?> cls = Class.forName(className);DBTable dbtable = cls.getAnnotation(DBTable.class);if(dbtable!=null){if(dbtable.name().length()<1){colunm = cls.getName();}else{colunm = dbtable.name();}}//-----------------------------------------------------------------------------------------ArrayList<String> list = new ArrayList<>();    for(Field f:cls.getDeclaredFields()){    System.out.println(f.getName());     Annotation[] anns =   f.getAnnotations();     if(anns[0] instanceof SQLString){    SQLString sqlString = (SQLString)anns[0];    if(sqlString.name().length()<1){    list.add(f.getName()+"   VARCHAR("+sqlString.value()+")");    }else{    list.add(sqlString.name()+"    VARCHAR(+"+sqlString.value()+")"+getConstraints(sqlString.constraints()));    }     }else if(anns[0] instanceof SQLInteger){     SQLInteger sqlInteger = (SQLInteger) anns[0];     if(sqlInteger.name().length()<1){     list.add(f.getName()+"   int("+sqlInteger.value()+")");     }else{     list.add(sqlInteger.name()+"    int("+sqlInteger.value()+")"+getConstraints(sqlInteger.constraints()));     }     }         }        //------------------------------------------------------------------------------------------    StringBuffer sqlCommand = new StringBuffer();   sqlCommand.append("Create   "+colunm +"{"+"\n");for(int i = 0;i<list.size()-1;i++){sqlCommand.append(list.get(i)+","+"\n");}sqlCommand.append(list.get(list.size()-1)+"\n"+"}");System.out.println(sqlCommand);}private static String getConstraints(Constraints constraints) {String str = null;if(!constraints.NULL()){str+="NULL";}else if(!constraints.unique()){str+="unqiue";}else if(!constraints.primaryKey()){str+="primarykey";}return str;}}

阅读全文

0 0