1 應用場景
項目中往往需要動態的創建一個表單，或者添加一個新的數據模板，這時候因為需要在運行時動態的創建表以及動態的維護表字段甚至表關系 使得普通java解決方案變得困難重重。
2 實現工具
Hibernate + Spring + Groovy +Freemarker
Hibernate 作用很簡單負責創建數據庫表這樣可以避免我們自己去寫復雜的sql和判斷。
Spring 作為橋梁起到連接紐帶的作用。
Groovy做為動態語言，在項目運行時根據模板創建訪問數據庫，或者控制層代碼。
Freamker 可以根據提前定義好的模板生成 hibernate配置文件，以及Groovy代碼。
3 實現原理
首先創建Form 和 FromAttribute 兩張表關系一對多。Form表記錄表單的名稱，類別，甚至是作為在動態生成表單時的css樣式信息。FromAttribute記錄表單字段信息，如名稱，類別等。有了表單以及表單項的信息後就可以創建數據庫表了。
測試代碼：
public void testGenerator() {
Form form = formService.getAll().get(0);
List<FormAttribute> list = formAttributeService
.getAttributeListByFormId(form.getId());
form.setFormAttributeList(list);
DbGenerator dg = new DbGenerator(form, dataSource);
dg.generator();
}
DbGenerator
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import javax.sql.DataSource;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
public class DbGenerator {
private DataSource dataSource;
protected Map root = new HashMap();
private static Logger log = LoggerFactory.getLogger(FormGenerator.class);
protected String path;
protected String packageName;
private Form form;
protected Configuration getConfig(String resource) {
Configuration cfg = new Configuration();
cfg.setDefaultEncoding("UTF-8");
cfg.setClassForTemplateLoading(this.getClass(), resource);
return cfg;
}
public DbGenerator(Form form ,DataSource dataSource) {
this.form = form;
this.dataSource = dataSource;
}
public void generator() {
if(null == form.getFormAttributeList() || form.getFormAttributeList().size() == 0){
return ;
}
Template t;
try {
t = getConfig("/template").getTemplate("hibernate.ftl");
Writer out = new StringWriter();
t.process(getMapContext(), out);
String xml = out.toString();
createTable(xml);
log.debug(xml);
} catch (IOException e) {
e.printStackTrace();
} catch (TemplateException e) {
e.printStackTrace();
}
}
@SuppressWarnings("unchecked")
Map getMapContext() {
root.put("entity", form);
return root;
}
public void createTable(String xml) {
org.hibernate.cfg.Configuration conf = new org.hibernate.cfg.Configuration();
conf.configure("/hibernate/hibernate.cfg.xml");
Properties extraProperties = new Properties();
extraProperties.put("hibernate.hbm2ddl.auto", "create");
conf.addProperties(extraProperties);
conf.addXML(xml);
SchemaExport dbExport;
try {
dbExport = new SchemaExport(conf, dataSource.getConnection());
// dbExport.setOutputFile(path);
dbExport.create(false, true);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class hibernateGenerator {
}
hibernate.ftl
<?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="${entity.name}"
table="`${entity.tableName}`"
dynamic-update="false"
dynamic-insert="false"
select-before-update="false"
optimistic-lock="version">
<id
name="id"
column="id"
type="java.lang.String"
unsaved-value="null">
<generator class="uuid" />
</id>
<#if entity.formAttributeList?exists>
<#list entity.formAttributeList as attr>
<#if attr.name == "id">
<#else>
<property
name="${attr.name}"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="`${attr.columnName}`"
length="${attr.length}"
not-null="false"
unique="false"
/>
</#if>
</#list>
</#if>
</class>
</hibernate-mapping>
hibernate.cfg.xml
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="dialect">org.hibernate.dialect.SQLServerDialect</property>
<property name="connection.driver_class">net.sourceforge.jtds.jdbc.Driver</property>
<property name="connection.url">jdbc:jtds:sqlserver://127.0.0.1:1433;databasename=struts;SelectMethod=cursor</property>
<property name="connection.username">sa</property>
<property name="connection.password">sa</property>
<property name="show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">update</property>
<!--
<mapping resource="hibernate/FormAttribute.hbm.xml" />
<mapping resource="hibernate/Form.hbm.xml" />
-->
</session-factory>
</hibernate-configuration>
創建好數據庫後 就要利用groovy動態創建訪問代碼了：先看測試代碼 再看具體實現：
public void testGroovy() {
Form form = formService.get("1");
List<FormAttribute> list = formAttributeService
.getAttributeListByFormId(form.getId());
form.setFormAttributeList(list);
FormGenerator fg = new FormGenerator(form);
String groovycode = fg.generator();
ClassLoader parent = getClass().getClassLoader();
GroovyClassLoader loader = new GroovyClassLoader(parent);
Class groovyClass = loader.parseClass(groovycode);
GroovyObject groovyObject = null;
try {
groovyObject = (GroovyObject) groovyClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
// map中key為formAttribute中描述該表單字段在數據庫中的名稱c_columnName
// 具體情況根據formAttribute而定
Map map = new HashMap();
map.put("name", "limq");
// 調用insert方法插入數據
int c = (Integer) groovyObject.invokeMethod("insert", map);
// 調用getAll方法獲得所有動態表中的數據
Object o = groovyObject.invokeMethod("getAll", null);
List list2 = (List) o;
Object obj = list2.get(0);
try {
String tname = (String) BeanUtils.getDeclaredProperty(obj, "name");
System.out.println(tname);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
}
// 調用search方法查詢動態表
List<Map> returnList = (List) groovyObject.invokeMethod("search", map);
for (Map map2 : returnList) {
// 同理此處根據FromAttribute而定
System.out.println(map2.get("id"));
System.out.println(map2.get("name"));
System.out.println(map2.get("type"));
}
}
FormGenerator ： 創建訪問數據庫Groovy代碼
public class FormGenerator {
protected Map root = new HashMap();
private static Logger log = LoggerFactory.getLogger(FormGenerator.class);
protected String path ;
protected String packageName ;
private Form form ;
protected Configuration getConfig(String resource) {
Configuration cfg = new Configuration();
cfg.setDefaultEncoding("UTF-8");
cfg.setClassForTemplateLoading(this.getClass(), resource);
return cfg;
}
public FormGenerator(Form form){
this.form = form;
}
public String generator(){
String returnstr = null;
Template t;
try {
t = getConfig("/template").getTemplate("FormService.ftl");
//Writer out = new OutputStreamWriter(new FileOutputStream(new File(path)),"UTF-8");
Writer out = new StringWriter();
t.process(getMapContext(), out);
returnstr = out.toString();
log.debug(returnstr);
} catch (IOException e) {
e.printStackTrace();
} catch (TemplateException e) {
e.printStackTrace();
}
return returnstr;
}
@SuppressWarnings("unchecked")
Map getMapContext() {
root.put("entity", form);
root.put("insert", SqlHelper.buildInsertStatement(form));
root.put("update", SqlHelper.buildUpdateStatement(form));
root.put("insertParameter", SqlHelper.buildInsertparameter(form));
root.put("updateParameter", SqlHelper.buildUpdateparameter(form));
root.put("delete", SqlHelper.buildDeleteStatement(form));
root.put("query", SqlHelper.buildQueryStatement(form));
return root;
}
}
FormService.ftl
import java.sql.ResultSet
import java.sql.SQLException
import java.sql.Types
import org.springframework.jdbc.core.RowMapper
import org.springframework.jdbc.core.RowMapperResultSetExtractor
import com.glnpu.sige.core.dao.DataSourceFactory
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;
class ${entity.name?cap_first}Dao {
def insert = '${insert}'
def delete = '${delete}'
def update = '${update}'
def int insert( entity){
def Object[] params = [${insertParameter}]
<#assign size = entity.formAttributeList?size/>
def int[] types=[<#list 1..size+1 as p>Types.VARCHAR,<#rt/></#list>]
return DataSourceFactory.getJdbcTemplate().update(insert, params, types)
}
def int update( entity){
def Object[] params = [${updateParameter}]
return DataSourceFactory.getJdbcTemplate().update(update, params)
}
def int delete(String entityId){
def Object[] params =[entityId]
return DataSourceFactory.getJdbcTemplate().update(delete, params)
}
def search(entity){
${query}
println(query);
return DataSourceFactory.getJdbcTemplate().queryForList(query);
}
}
以上代碼示意了如何利用 freemarker 生成 Groovy 和 hibernate 相關代碼，以及如何利用Groovy動態的對數據庫進行創建和增刪改查操作，了解以上的原理後就可以方便的在運行時利用freemarker生成表示層頁面以及代碼來進行展示。
