java注解演示 映射生成表 示例 来自thinking in java 4 20章部分代码
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;
/**
* 如果要令嵌入的@Constraints注解中的unique()元素为true 并以此作为constraints()元素的默认值
* 则需要如下定义该元素
* @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;
/**
* 相前资料请参考 thinking in java 第4版 20章
* @author lenovo
*
*/
public class TableCreator {
//解释注解 获得相应的值
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>();
//获取所有字段
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;
//如果是SqlInteger
if(annot[0] instanceof SqlInteger)
{
SqlInteger sInt=(SqlInteger)annot[0];
//如果没有指定名称 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()));
}
//如果是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);
*/
java注解演示 映射生成表 示例 来自thinking in java 4 20章部分代码,布布扣,bubuko.com