Hibernate自定义表单完全解决方案(无需重置SessionFactory)

最近开发的一个系统，需要在不更改代码和重启系统的情况下提供对用户自动建表的支持，由于系统应用了hibernate，所以在建表同时也要建立持久化对象以及对这些对象注册

数据库是不确定类型的,目前在比如数据库类型支持，还有对象关系支持上都很简单，不过在现有基础上进行扩展，都是可以实现的
实现步骤如下
建立class->生成hbm.xml->在Hibernate'config里面注册持久化类->通知SessionFactory持久化类的新增
1 准备
首先准备基础数据，我建立了几个类来对生成的表和属性做描述 这些描述都将作为传输传递给class生成方法和hbm.xml的生成方法
RenderClass 描述要生成的实体类 属性如下

className 类名
tableName 对应表名
properties 属性集合

RenderProperty 就是properties集合的内容 属性如下

name 属性名称
type java类型
field 字段名
primary 是否主键
sequence 对应ID生成的sequence
length 对应长度

2 生成class
采用ASM 生成

Java代码
/**  
 * 根据传入参数创建CLASS文件  
 *  
 * @param 类名  
 * @param 保存路径  
 * @param 属性描述  
 * @return Class  
 */  
public  Class build(String clsname,String savepath,Collection properties)   
{   
    Class cls = null;   
    try  
    {   
        String classname = BuildUtil.transferClassName(clsname);   
        ClassWriter cw = new ClassWriter(false);      
        //建立构造函数   
        cw.visit(V1_1, ACC_PUBLIC, classname, null, "java/lang/Object", null);      
        MethodVisitor mw = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);      
        mw.visitVarInsn(ALOAD, 0);      
        mw.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");      
        mw.visitInsn(RETURN);      
        mw.visitMaxs(1, 1);      
        mw.visitEnd();   
           
        BuildProperty property = null;   
        String propertytype = null;   
        String propertyname = null;;   
        //建立属性   
        Iterator iterator = properties.iterator();   
        while (iterator.hasNext())   
        {   
            //建立属性对应的类变量   
            property = (BuildProperty)iterator.next();   
            propertytype = BuildUtil.transferClassName(property.getType());   
            propertyname = WordUtils.capitalize(property.getName());   
            cw.visitField(ACC_PRIVATE, property.getName(), "L"+propertytype+";", null, null).visitEnd();   
            //建立get方法   
            mw = cw.visitMethod(ACC_PUBLIC, "get"+propertyname, "()L"+propertytype+";", null,    
            null);    
            mw.visitCode();    
            mw.visitVarInsn(ALOAD, 0);    
            mw    
            .visitFieldInsn(GETFIELD, classname, property.getName(),    
            "L"+propertytype+";");    
            mw.visitInsn(ARETURN);    
            mw.visitMaxs(1, 1);    
            mw.visitEnd();    
            //建立set方法   
            mw = cw.visitMethod(ACC_PUBLIC, "set"+propertyname, "(L"+propertytype+";)V",    
                    null, null);    
            mw.visitCode();    
            mw.visitVarInsn(ALOAD, 0);    
            mw.visitVarInsn(ALOAD, 1);    
            mw    
            .visitFieldInsn(PUTFIELD, classname, property.getName(),    
            "L"+propertytype+";");    
            mw.visitMaxs(2, 2);    
            mw.visitInsn(RETURN);    
            mw.visitEnd();    
        }   
           
        cw.visitEnd();   
  
        byte[] code = cw.toByteArray();    
        if (savepath!=null)   
        {     
            Assistant.createNewFile(savepath);   
            FileOutputStream fos = new FileOutputStream(savepath);      
            fos.write(code);      
            fos.close();      
        }   
        cls = this.defineClass(clsname, code, 0, code.length);   
        return cls;   
    }   
    catch (Throwable e)   
    {   
        e.printStackTrace();   
    }   
    return cls;   
}  
 /**
  * 根据传入参数创建CLASS文件
  *
  * @param 类名
  * @param 保存路径
  * @param 属性描述
  * @return Class
  */
 public  Class build(String clsname,String savepath,Collection properties)
 {
  Class cls = null;
  try
  {
   String classname = BuildUtil.transferClassName(clsname);
   ClassWriter cw = new ClassWriter(false);  
   //建立构造函数
   cw.visit(V1_1, ACC_PUBLIC, classname, null, "java/lang/Object", null);  
   MethodVisitor mw = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);  
   mw.visitVarInsn(ALOAD, 0);  
   mw.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");  
   mw.visitInsn(RETURN);  
   mw.visitMaxs(1, 1);  
   mw.visitEnd();
   
   BuildProperty property = null;
   String propertytype = null;
   String propertyname = null;;
   //建立属性
   Iterator iterator = properties.iterator();
   while (iterator.hasNext())
   {
    //建立属性对应的类变量
    property = (BuildProperty)iterator.next();
    propertytype = BuildUtil.transferClassName(property.getType());
    propertyname = WordUtils.capitalize(property.getName());
    cw.visitField(ACC_PRIVATE, property.getName(), "L"+propertytype+";", null, null).visitEnd();
    //建立get方法
       mw = cw.visitMethod(ACC_PUBLIC, "get"+propertyname, "()L"+propertytype+";", null,
       null);
       mw.visitCode();
       mw.visitVarInsn(ALOAD, 0);
       mw
       .visitFieldInsn(GETFIELD, classname, property.getName(),
       "L"+propertytype+";");
       mw.visitInsn(ARETURN);
       mw.visitMaxs(1, 1);
       mw.visitEnd();
       //建立set方法
       mw = cw.visitMethod(ACC_PUBLIC, "set"+propertyname, "(L"+propertytype+";)V",
         null, null);
       mw.visitCode();
       mw.visitVarInsn(ALOAD, 0);
       mw.visitVarInsn(ALOAD, 1);
       mw
       .visitFieldInsn(PUTFIELD, classname, property.getName(),
       "L"+propertytype+";");
       mw.visitMaxs(2, 2);
       mw.visitInsn(RETURN);
       mw.visitEnd();
   }
   
   cw.visitEnd();

      byte[] code = cw.toByteArray();
   if (savepath!=null)
   { 
    Assistant.createNewFile(savepath);
       FileOutputStream fos = new FileOutputStream(savepath);  
       fos.write(code);  
       fos.close();  
   }
   cls = this.defineClass(clsname, code, 0, code.length);
   return cls;
  }
  catch (Throwable e)
  {
   e.printStackTrace();
  }
  return cls;
 }
3 生成hbm.xml
生成这种事情，当然是交给模板了，我这里用的是Freemarker,在这里，我要感谢freemarker的开发组，感谢webwork 感谢XXCMS系统对freemarker以及其他模板语言的大力推广，，感谢。。。。（省略100字）
模板嘛，肯定不仅仅是应用在web环境的，看看源代码下的freemarker.cache包，恩，不错，freemarker团队确实是有一定“野心”的 首先是渲染的实现

Java代码
package com.mit.cooperate.core.asm.render;   
  
import java.io.File;   
import java.io.FileOutputStream;   
import java.io.PrintWriter;   
import java.io.StringWriter;   
  
import javax.servlet.ServletContext;   
  
import com.mit.cooperate.core.util.Assistant;   
  
import freemarker.cache.ClassTemplateLoader;   
import freemarker.template.Configuration;   
import freemarker.template.ObjectWrapper;   
import freemarker.template.SimpleHash;   
import freemarker.template.Template;   
import freemarker.template.TemplateExceptionHandler;   
/**  
 * freeMarker模板渲染  
 * @author courser.tijichen  
 */  
public class FreemarkerRender implements Render{   
       
    private Configuration templateconfig;   
       
    public  FreemarkerRender()   
    {   
        this.initialize();   
    }   
    /**  
     * 初始化freemarker配置  
     *  
     */  
    public void initialize()   
    {   
        try  
        {   
            if (templateconfig==null)   
            {   
                templateconfig = new Configuration();   
                templateconfig.setTemplateExceptionHandler(TemplateExceptionHandler.HTML_DEBUG_HANDLER);   
                templateconfig.setObjectWrapper(ObjectWrapper.DEFAULT_WRAPPER);   
                templateconfig.setTemplateLoader(new ClassTemplateLoader(this.getClass(),"/"));   
                templateconfig.setTemplateUpdateDelay(1200);   
                templateconfig.setDefaultEncoding("gb2312");   
                templateconfig.setLocale(new java.util.Locale("zh_CN"));   
                templateconfig.setNumberFormat("0.##########");   
            }   
        }   
        catch (Exception e)   
        {}   
    }   
    /**  
     * 渲染  
     *  
     */  
    public void render(RenderClass target,String template,String outpath)   
    {   
        try  
        {   
            StringWriter writer = new StringWriter();   
            Template tl = templateconfig.getTemplate(   
                    template,   
                    templateconfig.getLocale());   
            SimpleHash root = new SimpleHash();   
            root.put("entity", target);   
            tl.process(root, writer);   
            Assistant.createNewFile(outpath);   
            FileOutputStream fos = new FileOutputStream(outpath);   
            PrintWriter pwriter = new PrintWriter(fos);   
            pwriter.write(writer.toString());   
            pwriter.close();   
            fos.close();      
        }   
        catch (Exception ex)   
        {   
            ex.printStackTrace();   
        }   
    }   
}  
package com.mit.cooperate.core.asm.render;

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.ServletContext;

import com.mit.cooperate.core.util.Assistant;

import freemarker.cache.ClassTemplateLoader;
import freemarker.template.Configuration;
import freemarker.template.ObjectWrapper;
import freemarker.template.SimpleHash;
import freemarker.template.Template;
import freemarker.template.TemplateExceptionHandler;
/**
 * freeMarker模板渲染
 * @author courser.tijichen
 */
public class FreemarkerRender implements Render{
 
 private Configuration templateconfig;
 
 public  FreemarkerRender()
 {
  this.initialize();
 }
 /**
  * 初始化freemarker配置
  *
  */
 public void initialize()
 {
  try
  {
   if (templateconfig==null)
   {
    templateconfig = new Configuration();
    templateconfig.setTemplateExceptionHandler(TemplateExceptionHandler.HTML_DEBUG_HANDLER);
    templateconfig.setObjectWrapper(ObjectWrapper.DEFAULT_WRAPPER);
    templateconfig.setTemplateLoader(new ClassTemplateLoader(this.getClass(),"/"));
    templateconfig.setTemplateUpdateDelay(1200);
    templateconfig.setDefaultEncoding("gb2312");
    templateconfig.setLocale(new java.util.Locale("zh_CN"));
    templateconfig.setNumberFormat("0.##########");
   }
  }
  catch (Exception e)
  {}
 }
 /**
  * 渲染
  *
  */
 public void render(RenderClass target,String template,String outpath)
 {
  try
  {
   StringWriter writer = new StringWriter();
   Template tl = templateconfig.getTemplate(
     template,
     templateconfig.getLocale());
   SimpleHash root = new SimpleHash();
   root.put("entity", target);
   tl.process(root, writer);
   Assistant.createNewFile(outpath);
   FileOutputStream fos = new FileOutputStream(outpath);
   PrintWriter pwriter = new PrintWriter(fos);
   pwriter.write(writer.toString());
   pwriter.close();
   fos.close();  
  }
  catch (Exception ex)
  {
   ex.printStackTrace();
  }
 }
}
然后就是准备模板了，首先声明，我这个模板写得简单粗陋之极，不过粗陋简单不正是人渣偶的终极处世之道么，何况只实现几个简单功能，仅仅是针对测试而已嘛，何必搞得那么正规严肃了，嘿嘿

Html代码
<?xml version="1.0" encoding="utf-8"?>  
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"   
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">  
<hibernate-mapping>  
    <class name="${entity.className}" table="${entity.tableName}">  
        <#if entity.properties?exists>  
            <#list entity.properties as property>  
                <#if property.primary>  
                    <id name="${property.name}" type="${property.type}">  
                <#else>  
                    <property name="${property.name}" type="${property.type}">  
                </#if>  
                <#if property.type=="java.lang.String">  
                    <column name="${property.field?upper_case}" <#if property.length?exists>length="${property.length}"</#if>></column>  
                <#elseif property.type=="java.util.Date">  
                        <column name="${property.field?upper_case}" length=7></column>  
                <#elseif property.type=="java.lang.Long" || property.type=="java.lang.Integer"   
                    || property.type=="java.lang.Short">  
                        <column name="${property.field?upper_case}" <#if property.length?exists>precision="${property.length}"</#if> scale="0"></column>  
                </#if>  
                <#if property.primary==true>  
                    <#if property.sequence?exists>  
                        <generator class="sequence">  
                            <param name="sequence">${property.sequence}</param>  
                        </generator>  
                    </#if>  
                    </id>  
                <#else>  
                    </property>  
                </#if>  
            </#list>  
        </#if>  
    </class>  
</hibernate-mapping>  
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="${entity.className}" table="${entity.tableName}">
     <#if entity.properties?exists>
   <#list entity.properties as property>
    <#if property.primary>
     <id name="${property.name}" type="${property.type}">
    <#else>
     <property name="${property.name}" type="${property.type}">
    </#if>
    <#if property.type=="java.lang.String">
     <column name="${property.field?upper_case}" <#if property.length?exists>length="${property.length}"</#if>></column>
    <#elseif property.type=="java.util.Date">
      <column name="${property.field?upper_case}" length=7></column>
    <#elseif property.type=="java.lang.Long" || property.type=="java.lang.Integer"
     || property.type=="java.lang.Short">
      <column name="${property.field?upper_case}" <#if property.length?exists>precision="${property.length}"</#if> scale="0"></column>
    </#if>
    <#if property.primary==true>
     <#if property.sequence?exists>
      <generator class="sequence">
       <param name="sequence">${property.sequence}</param>
      </generator>
     </#if>
     </id>
    <#else>
     </property>
    </#if>
   </#list>
  </#if>
    </class>
</hibernate-mapping>
4 注册
首先是对生成的hbm.xml的注册，比如，我获取倒Hibernate的一个config以后

Java代码
URL  url = this.getClass().getResource("/com/mit/test/person.hbm.xml");   
config.addURL(url);  
URL  url = this.getClass().getResource("/com/mit/test/person.hbm.xml");
config.addURL(url);
然后就是要通知sessionFactory，新增了持久类，目前很多方法都是重启sessionfactory，就是关闭当前 sessionFactory ，然后根据config build一个新的sessionFactory出来，但是，这种情况感觉总不那么完美，虽然这个过程持续不到多长时间，但用户每增一个表就close然后build一个，单说用户体验，人家正在提交数据了，你把这个给close了....
但目前hibernate包的 sessionFactory 确实没提供这种对持久类的add支持，XX伟人说过：没有条件 创造条件也要上，于是乎，拿起你的键盘，启动 editplus，向hibernate3的源码砍去。。

其实，改动地方也不大。

Java代码
一是，改动Configuration,三句话   
    public Mapping getMapping()   
    {   
        return this.mapping;   
    }  
一是，改动Configuration,三句话
 public Mapping getMapping()
 {
  return this.mapping;
 }
然后是SessionFactoryImpl 我们要让他知道，这个世界上还存在很多未知的来客，需要你去主动了解。。。。
增加代码如下

Java代码
public void addPersistentClass(PersistentClass model,Mapping mapping)   
{   
    if ( !model.isInherited() ) {   
        IdentifierGenerator generator = model.getIdentifier().createIdentifierGenerator(   
                settings.getDialect(),   
                settings.getDefaultCatalogName(),   
                settings.getDefaultSchemaName(),   
                (RootClass) model   
        );   
        if (!identifierGenerators.containsKey(model.getEntityName()))   
            identifierGenerators.put( model.getEntityName(), generator );   
    }   
       
    model.prepareTemporaryTables( mapping, settings.getDialect() );   
    String cacheRegion = model.getRootClass().getCacheRegionName();   
  
    CacheConcurrencyStrategy cache = CacheFactory.createCache(   
                model.getCacheConcurrencyStrategy(),   
                cacheRegion,   
                model.isMutable(),   
                settings,   
                properties   
            );   
    if (cache!=null)   
        allCacheRegions.put( cache.getRegionName(), cache.getCache() );   
           
       
    EntityPersister cp = PersisterFactory.createClassPersister(model, cache, this, mapping);   
    if ( cache != null && cache.getCache() instanceof OptimisticCache ) {   
        ( ( OptimisticCache ) cache.getCache() ).setSource( cp );   
    }   
    entityPersisters.put( model.getEntityName(), cp );   
}  
 public void addPersistentClass(PersistentClass model,Mapping mapping)
 {
  if ( !model.isInherited() ) {
   IdentifierGenerator generator = model.getIdentifier().createIdentifierGenerator(
     settings.getDialect(),
           settings.getDefaultCatalogName(),
           settings.getDefaultSchemaName(),
           (RootClass) model
   );
   if (!identifierGenerators.containsKey(model.getEntityName()))
    identifierGenerators.put( model.getEntityName(), generator );
  }
  
  model.prepareTemporaryTables( mapping, settings.getDialect() );
  String cacheRegion = model.getRootClass().getCacheRegionName();
 
  CacheConcurrencyStrategy cache = CacheFactory.createCache(
     model.getCacheConcurrencyStrategy(),
           cacheRegion,
           model.isMutable(),
           settings,
           properties
    );
  if (cache!=null)
   allCacheRegions.put( cache.getRegionName(), cache.getCache() );
   
  
  EntityPersister cp = PersisterFactory.createClassPersister(model, cache, this, mapping);
  if ( cache != null && cache.getCache() instanceof OptimisticCache ) {
   ( ( OptimisticCache ) cache.getCache() ).setSource( cp );
  }
  entityPersisters.put( model.getEntityName(), cp );
 }
最后遗留的是hbm.xml在cfg.xml的注册，以保证系统重启后可以顺利加载新增的持久化配置

Java代码
/**  
 * 把hbm.xml的路径加入到cfg.xml的mapping结点  
 *  
 * @param cfg.xml的路径  
 * @param hbm.xml的路径  
 */  
public static void updateHbmCfg(URL url,String hbm)   
{   
    try  
    {   
        SAXReader reader = new SAXReader();   
        Document doc = reader.read(url);   
        Element element = (Element)doc.getRootElement()   
        .selectSingleNode("session-factory");   
           
        Element hbmnode = element.addElement("mapping");   
        hbmnode.addAttribute("resource", hbm);   
        String filepath = url.getFile();   
        if (filepath.charAt(0)=='/')   
            filepath = filepath.substring(1);   
        FileOutputStream outputstream = new FileOutputStream(filepath);   
        XMLWriter writer = new XMLWriter(outputstream);   
        writer.write(doc);   
        outputstream.close();   
    }   
    catch (Exception e)   
    {   
        e.printStackTrace();   
    }   
}  
 /**
  * 把hbm.xml的路径加入到cfg.xml的mapping结点
  *
  * @param cfg.xml的路径
  * @param hbm.xml的路径
  */
 public static void updateHbmCfg(URL url,String hbm)
 {
  try
  {
   SAXReader reader = new SAXReader();
   Document doc = reader.read(url);
   Element element = (Element)doc.getRootElement()
   .selectSingleNode("session-factory");
   
   Element hbmnode = element.addElement("mapping");
   hbmnode.addAttribute("resource", hbm);
   String filepath = url.getFile();
   if (filepath.charAt(0)=='/')
    filepath = filepath.substring(1);
   FileOutputStream outputstream = new FileOutputStream(filepath);
   XMLWriter writer = new XMLWriter(outputstream);
   writer.write(doc);
   outputstream.close();
  }
  catch (Exception e)
  {
   e.printStackTrace();
  }
 }Java代码
大功告成 ，先运行一个小周天  
大功告成 ，先运行一个小周天
最后是总结测试，写个junit 搞定 代码如下:

Java代码
package com.mit.cooperate.core.hibernate;   
  
import junit.framework.TestCase;   
  
import java.net.URL;   
import java.util.ArrayList;   
  
import org.apache.commons.beanutils.PropertyUtils;   
  
import org.hibernate.Session;   
import org.hibernate.cfg.Configuration;   
import org.hibernate.SessionFactory;   
import org.hibernate.tool.hbm2ddl.SchemaExport;   
import org.hibernate.impl.SessionFactoryImpl;   
import org.hibernate.mapping.PersistentClass;   
import org.hibernate.Transaction;   
  
import com.mit.cooperate.core.asm.*;   
import com.mit.cooperate.core.asm.render.*;   
  
public class HibernateTest extends TestCase {   
       
    private Configuration config;   
    private SessionFactory factory;   
       
    public void setUp()   
    {   
        URL  url = this.getClass().getResource("/com/mit/cooperate/core/hibernate/hibernate.cfg.xml");   
        config = new Configuration().configure(url);   
        factory = config.buildSessionFactory();   
    }   
       
    public void testBuild() throws Exception   
    {   
        //持久类对象描述   
        RenderClass rc = new RenderClass();   
        ArrayList list = new ArrayList();   
           
        RenderProperty property = new RenderProperty();   
        //添加主键   
        property.setName("oid");   
        property.setField("oid");   
        property.setLength(new Integer(15));   
        property.setPrimary(true);   
        property.setType(Long.class.getName());   
        property.setSequence("SEQ_PERSON");   
           
        list.add(property);   
        //添加一个name字段   
        property = new RenderProperty();   
        property.setName("name");   
        property.setType(String.class.getName());   
        property.setField("name");   
        property.setLength(new Integer(20));   
           
        list.add(property);   
           
        rc.setProperties(list);   
        //类名   
        rc.setClassName("com.mit.test.Person");   
        rc.setTableName("person");   
        //开始生成class   
        POBuildUtil util = new POBuildUtil();   
        util.build(rc.getClassName(),"E://cpc//source//cooperateCore//com//mit//test//Person.class",list);   
        //实例化一个person   
        Object person = Class.forName("com.mit.test.Person").newInstance();//hbmcls.newInstance();   
           
        //开始生成hbm.xml   
        FreemarkerRender render = new FreemarkerRender();   
        render.render(rc, Templates.TEMPLATE_HIBERNATE3, "E://cpc//source//cooperateCore//com//mit//test//person.hbm.xml");   
        URL  url = this.getClass().getResource("/com/mit/test/person.hbm.xml");   
        config.addURL(url);   
        //更新hibernate.cfg.xml   
        HibernateUtil.updateHbmCfg( this.getClass().getResource("/com/mit/cooperate/core/hibernate/hibernate.cfg.xml"), "com/mit/test/person.hbm.xml");   
           
        PersistentClass model = config.getClassMapping("com.mit.test.Person");   
        //sessionFactory哪下子，快接纳person爷爷进去   
        ((SessionFactoryImpl)factory).addPersistentClass(model, config.getMapping());   
        //生成数据库   
        SchemaExport export = new SchemaExport(config,((SessionFactoryImpl)factory).getSettings());   
        export.execute(true, true,false,true);   
        //测试一下，随便给个名字什么的   
        PropertyUtils.setProperty(person, "name", "chenzhi");   
        Session session = factory.openSession();   
        Transaction tran = session.beginTransaction();   
        try  
        {   
            //保存   
            session.save(person);   
            tran.commit();   
        }   
        catch (Exception e)   
        {   
            e.printStackTrace();   
            tran.rollback();   
        }   
        finally  
        {   
            session.close();   
        }   
    }   
       
    public void tearDown()   
    {   
        factory.close();   
    }   
       
       
}

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/zzr173/archive/2009/09/23/4584292.aspx