SpringBoot+JPA+Freemarker 生成动态SQL
在实际开发中，有时候会遇到复杂的统计SQL，这时候Hibernate并不能很好的满足我们的需求，一方面SQL语句写在代码中不美观，可读性比较差，另一方面不方便修改SQL语句。
如果可以像mybaits一样写在XML中的话，就方便许多了。
采用Freemarker模板就可以达到将SQL写在XML文件中的功能。
一、pom引用
org.springframework.boot
spring-boot-starter-data-jpa
org.springframework.boot
spring-boot-starter-logging
org.springframework.boot
spring-boot-starter-freemarker
org.springframework.boot
spring-boot-starter-jdbc
org.springframework.boot
spring-boot-starter-log4j2
二、写个DTD文件，定义XML文件格式
三、DTD解析器
public class DynamicStatementDTDEntityResolver implements EntityResolver {
private static final Logger LOGGER = LoggerFactory.getLogger(DynamicStatementDTDEntityResolver.class);
private static final String HOP_DYNAMIC_STATEMENT = "http://www.wongws.com/dtd/";
public InputSource resolveEntity(String publicId, String systemId) {
InputSource source = null; // returning null triggers default behavior
if (systemId != null) {
LOGGER.debug("trying to resolve system-id [" + systemId + "]");
if (systemId.startsWith(HOP_DYNAMIC_STATEMENT)) {
LOGGER.debug(
"recognized hop dyanmic statement namespace; attempting to resolve on classpath under com/haier/openplatform/dao/hibernate/");
source = resolveOnClassPath(publicId, systemId, HOP_DYNAMIC_STATEMENT);
}
}
return source;
}
private InputSource resolveOnClassPath(String publicId, String systemId, String namespace) {
InputSource source = null;
String path = "dtd/" + systemId.substring(namespace.length());
InputStream dtdStream = resolveInHibernateNamespace(path);
if (dtdStream == null) {
LOGGER.debug("unable to locate [" + systemId + "] on classpath");
if (systemId.substring(namespace.length()).indexOf("2.0") > -1) {
LOGGER.error("Don't use old DTDs, read the Hibernate 3.x Migration Guide!");
}
} else {
LOGGER.debug("located [" + systemId + "] in classpath");
source = new InputSource(dtdStream);
source.setPublicId(publicId);
source.setSystemId(systemId);
}
return source;
}
protected InputStream resolveInHibernateNamespace(String path) {
return this.getClass().getClassLoader().getResourceAsStream(path);
}
}
四、构造存储动态SQL的对象
public class StatementTemplate {
public enum TYPE {
/** hql 查询 */
HQL,
/** sql 查询 */
SQL
}
public StatementTemplate() {
}
public StatementTemplate(TYPE type, Template template) {
this.type = type;
this.template = template;
}
private TYPE type;
private Template template;
public TYPE getType() {
return type;
}
public void setType(TYPE type) {
this.type = type;
}
public Template getTemplate() {
return template;
}
public void setTemplate(Template template) {
this.template = template;
}
}
五、构造动态SQL加载器
public class DefaultDynamicHibernateStatementBuilder implements DynamicHibernateStatementBuilder, ResourceLoaderAware {
private static final Logger LOGGER = LoggerFactory.getLogger(DefaultDynamicHibernateStatementBuilder.class);
private Map namedHQLQueries;
private Map namedSQLQueries;
private String[] fileNames = new String[0];
private ResourceLoader resourceLoader;
private EntityResolver entityResolver = new DynamicStatementDTDEntityResolver();
/**
* 查询语句名称缓存，不允许重复
*/
private Set nameCache = new HashSet();
public void setFileNames(String[] fileNames) {
this.fileNames = fileNames;
}
@Override
public Map getNamedHQLQueries() {
return namedHQLQueries;
}
@Override
public Map getNamedSQLQueries() {
return namedSQLQueries;
}
@Override
public void init() throws IOException {
namedHQLQueries = new HashMap();
namedSQLQueries = new HashMap();
boolean flag = this.resourceLoader instanceof ResourcePatternResolver;
for (String file : fileNames) {
if (flag) {
Resource[] resources = ((ResourcePatternResolver) this.resourceLoader).getResources(file);
buildMap(resources);
} else {
Resource resource = resourceLoader.getResource(file);
buildMap(resource);
}
}
// clear name cache
nameCache.clear();
}
@Override
public void setResourceLoader(ResourceLoader resourceLoader) {
this.resourceLoader = resourceLoader;
}
private void buildMap(Resource[] resources) {
if (resources == null) {
return;
}
for (Resource resource : resources) {
buildMap(resource);
}
}
@SuppressWarnings({ "rawtypes" })
private void buildMap(Resource resource) {
InputSource inputSource = null;
try {
inputSource = new InputSource(resource.getInputStream());
XmlDocument metadataXml = readMappingDocument(entityResolver, inputSource,
new OriginImpl("file", resource.getFilename()));
if (isDynamicStatementXml(metadataXml)) {
final Document doc = metadataXml.getDocumentTree();
final Element dynamicHibernateStatement = doc.getRootElement();
Iterator rootChildren = dynamicHibernateStatement.elementIterator();
while (rootChildren.hasNext()) {
final Element element = (Element) rootChildren.next();
final String elementName = element.getName();
if ("sql-query".equals(elementName)) {
putStatementToCacheMap(resource, element, namedSQLQueries);
} else if ("hql-query".equals(elementName)) {
putStatementToCacheMap(resource, element, namedHQLQueries);
}
}
}
} catch (Exception e) {
LOGGER.error(e.toString());
throw new RuntimeException(e);
} finally {
if (inputSource != null && inputSource.getByteStream() != null) {
try {
inputSource.getByteStream().close();
} catch (IOException e) {
LOGGER.error(e.toString());
throw new RuntimeException(e);
}
}
}
}
private void putStatementToCacheMap(Resource resource, final Element element, Map statementMap)
throws Exception {
String sqlQueryName = element.attribute("name").getText();
Validate.notEmpty(sqlQueryName);
if (nameCache.contains(sqlQueryName)) {
throw new RuntimeException("重复的sql-query/hql-query语句定义在文件:" + resource.getURI() + "中，必须保证name的唯一.");
}
nameCache.add(sqlQueryName);
String queryText = element.getText();
statementMap.put(sqlQueryName, queryText);
}
private static boolean isDynamicStatementXml(XmlDocument xmlDocument) {
return "dynamic-hibernate-statement".equals(xmlDocument.getDocumentTree().getRootElement().getName());
}
public XmlDocument readMappingDocument(EntityResolver entityResolver, InputSource source, Origin origin) {
return legacyReadMappingDocument(entityResolver, source, origin);
// return readMappingDocument( source, origin );
}
private XmlDocument legacyReadMappingDocument(EntityResolver entityResolver, InputSource source, Origin origin) {
// IMPL NOTE : this is the legacy logic as pulled from the old
// AnnotationConfiguration code
Exception failure;
ErrorLogger errorHandler = new ErrorLogger();
SAXReader saxReader = new SAXReader();
saxReader.setEntityResolver(entityResolver);
saxReader.setErrorHandler(errorHandler);
saxReader.setMergeAdjacentText(true);
saxReader.setValidation(true);
Document document = null;
try {
// first try with orm 2.1 xsd validation
setValidationFor(saxReader, "orm_2_1.xsd");
document = saxReader.read(source);
if (errorHandler.hasErrors()) {
throw errorHandler.getErrors().get(0);
}
return new XmlDocumentImpl(document, origin.getType(), origin.getName());
} catch (Exception e) {
LOGGER.debug("Problem parsing XML using orm 2.1 xsd, trying 2.0 xsd : {}", e.getMessage());
failure = e;
errorHandler.reset();
if (document != null) {
// next try with orm 2.0 xsd validation
try {
setValidationFor(saxReader, "orm_2_0.xsd");
document = saxReader.read(new StringReader(document.asXML()));
if (errorHandler.hasErrors()) {
errorHandler.logErrors();
throw errorHandler.getErrors().get(0);
}
return new XmlDocumentImpl(document, origin.getType(), origin.getName());
} catch (Exception e2) {
LOGGER.debug("Problem parsing XML using orm 2.0 xsd, trying 1.0 xsd : {}", e2.getMessage());
errorHandler.reset();
if (document != null) {
// next try with orm 1.0 xsd validation
try {
setValidationFor(saxReader, "orm_1_0.xsd");
document = saxReader.read(new StringReader(document.asXML()));
if (errorHandler.hasErrors()) {
errorHandler.logErrors();
throw errorHandler.getErrors().get(0);
}
return new XmlDocumentImpl(document, origin.getType(), origin.getName());
} catch (Exception e3) {
LOGGER.debug("Problem parsing XML using orm 1.0 xsd : {}", e3.getMessage());
}
}
}
}
}
throw new InvalidMappingException("Unable to read XML", origin.getType(), origin.getName(), failure);
}
private void setValidationFor(SAXReader saxReader, String xsd) {
try {
saxReader.setFeature("http://apache.org/xml/features/validation/schema", true);
// saxReader.setFeature( "http://apache.org/xml/features/validation/dynamic",
// true );
if ("orm_2_1.xsd".equals(xsd)) {
saxReader.setProperty("http://apache.org/xml/properties/schema/external-schemaLocation",
"http://xmlns.jcp.org/xml/ns/persistence/orm " + xsd);
} else {
saxReader.setProperty("http://apache.org/xml/properties/schema/external-schemaLocation",
"http://java.sun.com/xml/ns/persistence/orm " + xsd);
}
} catch (SAXException e) {
saxReader.setValidation(false);
}
}
}
public interface DynamicHibernateStatementBuilder {
/**
* hql语句map
*
* @return
*/
Map getNamedHQLQueries();
/**
* sql语句map
*
* @return
*/
Map getNamedSQLQueries();
/**
* 初始化
*
* @throws IOException
*/
void init() throws IOException;
void setFileNames(String[] fileNames);
void setResourceLoader(ResourceLoader resourceLoader);
}
六、利用Freemarker模板书写动态SQL
and t.password=${password}
]]>
以上就是功能实现的关键代码，但是利用Freemarker有个问题，就是没法解决SQL注入的问题，这里我的操作就是可以使用Freemarker生成动态SQL，然后再利用JdbcTemplate或NamedParameterJdbcTemplate来执行SQL。如将上面的SQL改写成这样：
and t.password=:password
]]>
这样的话就可以绕过Freemarker的占位符使用，然后再通过NamedParameterJdbcTemplate执行SQL。
当然实际SQL不可能这么简单，肯定会遇到Map或者List等问题，这些只要网上查询Freemarker的语法，就能迎刃而解。
下面奉上源码，由于这只是个Demo，代码实在是粗制滥造了点，但是功能还是能够实现的，在com.example.demo下的DemoApplicationTests类上，运行Junit Test。当然，要是实现mysql访问，还得自己配数据库连接。
https://download.csdn.net/download/dashuaigege642/10681049
参考：
https://blog.csdn.net/crazycoder2010/article/details/7414152