java注意事项演示 地图产生表 演示样本  来自thinking in java 4 20代码的章

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package org.rui.annotation.database;

import java.lang.annotation.*;

/**

 * 生成一个数据库表

 * @author lenovo

 *

 */

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

public @interface DBTable {

  public String name() default "";

}

package org.rui.annotation.database;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

 * sql类型

 * @author lenovo

 *

 */

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

public @interface SQLString {

	int value() default 0;

	String name() default "";

	Constraints constraints() default @Constraints;

}

package org.rui.annotation.database;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

 *  sql类型

 * @author lenovo

 *

 */

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

public @interface SqlInteger {

	int value() default 0;

	String name() default "";

	Constraints constraints() default @Constraints;

}

package org.rui.annotation.database;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

 * javaBean域准备的注解

 * @author lenovo

 *

 */

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

public @interface Constraints {

  boolean primaryKey() default false;

  boolean allowNull() default true;

  boolean unique() default false;

}

package org.rui.annotation.database;

/**

 * 假设要令嵌入的@Constraints注解中的unique()元素为true 并以此作为constraints()元素的默认值

 * 则须要例如以下定义该元素

 * @author lenovo

 *

 */

public @interface Uniqueness {

	Constraints constraints() default @Constraints(unique=true);

}

package org.rui.annotation.database;

@DBTable(name="MEMBER")

public class Member {

	@SQLString(30)	String firstName;

	@SQLString(50) String lastName;

	@SqlInteger Integer age;

	@SQLString(value=30,constraints=@Constraints(primaryKey=true))

	String handle;

	static int memberCount;

	//get

	public String getFirstName() {

		return firstName;

	}

	public String getLastName() {

		return lastName;

	}

	public Integer getAge() {

		return age;

	}

	public String getHandle() {

		return handle;

	}

	@Override

	public String toString()

	{

		return handle;

	}

}

package org.rui.annotation.database;

import java.io.ObjectInputStream.GetField;

import java.lang.annotation.Annotation;

import java.lang.reflect.Field;

import java.util.ArrayList;

import java.util.List;

/**

 * 相前资料请參考 thinking in  java 第4版 20章

 * @author lenovo

 *

 */

public class TableCreator {

	//解释注解 获得对应的值

	public static String getConstraints(Constraints con)

	{

		String constraints="";

		if(con.allowNull())

			constraints+="NOT NULL";

		if(con.primaryKey())

			constraints+="PRIMARY KEY";

		if(con.unique())

			constraints+="UNIQUE";

		return constraints;

	}

	public static void main(String[] args) throws ClassNotFoundException {

		String[] arr=new String[]{"org.rui.annotation.database.Member"};

		if (arr.length<1)

		{

			System.out.println("0000");

			System.exit(0);

		}

		for(String className:arr)

		{

			Class<?> clzz=Class.forName(className);

			DBTable table=clzz.getAnnotation(DBTable.class);

			if(table==null)

			{

				System.out.println("dbtable annotaions in class:"+className);

				continue;

			}

			String tableName=table.name();

			if(tableName.length()<1)

				tableName=clzz.getName().toUpperCase();

			 //结果集合

			 List<String> columnDefs=new ArrayList<String>();

			//获取全部字段

			for(Field f:clzz.getDeclaredFields())

			{

				String columnName =null;

				//获取字段上面的注解

				Annotation[] annot=f.getAnnotations();

				if(annot.length<1)continue;

				//假设是SqlInteger

				if(annot[0] instanceof SqlInteger)

				{

					SqlInteger sInt=(SqlInteger)annot[0];

					//假设没有指定名称    使用字段名称

					if(sInt.name().length()<1)

					{

						columnName=f.getName().toUpperCase();

					}else

					{

						columnName=sInt.name();

					}

					columnDefs.add(columnName+" INT"+getConstraints(sInt.constraints()));

				}

				//假设是string 内型

				if(annot[0] instanceof SQLString)

				{

					SQLString sStr=(SQLString)annot[0];

					if(sStr.name().length()<1)

					{

						columnName=f.getName().toUpperCase();

					}else

					{

						columnName=sStr.name();

					}

					columnDefs.add(columnName+" VARCHAR("+sStr.value()+")"+

					getConstraints(sStr.constraints()));

				}

				StringBuilder sql=new StringBuilder("CREATE TABLE "+tableName+"( ");

				for(String c:columnDefs)

				{

					sql.append("\n   "+c+",");//拼接字段

					//remove trailing comma

					String tableCreate=sql.substring(0,sql.length()-1)+");";

					System.out.println("table ceration sql fro "+className+" is :\n "+tableCreate);

				}

			}

		}

	}

}

/**output:

 table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL,

   AGE INTNOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL,

   AGE INTNOT NULL);

table ceration sql fro org.rui.annotation.database.Member is :

 CREATE TABLE MEMBER(

   FIRSTNAME VARCHAR(30)NOT NULL,

   LASTNAME VARCHAR(50)NOT NULL,

   AGE INTNOT NULL,

   HANDLE VARCHAR(30)NOT NULLPRIMARY KEY);

 */