1 應(yīng)用場景
項目中往往需要動態(tài)的創(chuàng)建一個表單，或者添加一個新的數(shù)據(jù)模板，這時候因為需要在運行時動態(tài)的創(chuàng)建表以及動態(tài)的維護表字段甚至表關(guān)系 使得普通java解決方案變得困難重重。
2 實現(xiàn)工具
Hibernate + Spring + Groovy +Freemarker
Hibernate 作用很簡單負責(zé)創(chuàng)建數(shù)據(jù)庫表這樣可以避免我們自己去寫復(fù)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(tài)語言，在項目運行時根據(jù)模板創(chuàng)建訪問數(shù)據(jù)庫，或者控制層代碼。
Freamker 可以根據(jù)提前定義好的模板生成 hibernate配置文件，以及Groovy代碼。
3 實現(xiàn)原理
首先創(chuàng)建Form 和 FromAttribute 兩張表關(guān)系一對多。Form表記錄表單的名稱，類別，甚至是作為在動態(tài)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后就可以創(chuàng)建數(shù)據(jù)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();
}
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 {
}
<?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(chuàng)建好數(shù)據(jù)庫后 就要利用groovy動態(tài)創(chuàng)建訪問代碼了：先看測試代碼 再看具體實現(xiàn)：
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(shù)據(jù)庫中的名稱c_columnName
// 具體情況根據(jù)formAttribute而定
Map map = new HashMap();
map.put("name", "limq");
// 調(diào)用insert方法插入數(shù)據(jù)
int c = (Integer) groovyObject.invokeMethod("insert", map);
// 調(diào)用getAll方法獲得所有動態(tài)表中的數(shù)據(jù)
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(diào)用search方法查詢動態(tài)表
List<Map> returnList = (List) groovyObject.invokeMethod("search", map);
for (Map map2 : returnList) {
// 同理此處根據(jù)FromAttribute而定
System.out.println(map2.get("id"));
System.out.println(map2.get("name"));
System.out.println(map2.get("type"));
}
}
FormGenerator ： 創(chuàng)建訪問數(shù)據(jù)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;
}
}
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(guān)代碼，以及如何利用Groovy動態(tài)的對數(shù)據(jù)庫進行創(chuàng)建和增刪改查操作，了解以上的原理后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。