打算抄袭一下MyBatis的Java注解方式配置,添加到在正在开发的持久层工具里,只需要定义一个接口方法,就可以用一个动态代理来使用它,这种方式的优点是可以利用Java的导舤功能快速定位SQL,比文本方式保存的模板定位方便,而且方法名和参数都是Java强类型,支持重构:
@Select("select * from users where id = #{id}") User getUserById(Integer id);
但还是老问题,Java对多行文本的支持太差,MyBatis的解决方法个人不是太喜欢,破坏了SQL的可读性:
private String selectPersonSql() { return new SQL() {{ SELECT("P.ID, P.USERNAME, P.PASSWORD, P.FULL_NAME"); SELECT("P.LAST_NAME, P.CREATED_ON, P.UPDATED_ON"); FROM("PERSON P"); FROM("ACCOUNT A"); INNER_JOIN("DEPARTMENT D on D.ID = P.DEPARTMENT_ID"); INNER_JOIN("COMPANY C on D.COMPANY_ID = C.ID"); WHERE("P.ID = A.ID"); WHERE("P.FIRST_NAME like ?"); OR(); WHERE("P.LAST_NAME like ?"); GROUP_BY("P.ID"); HAVING("P.LAST_NAME like ?"); OR(); HAVING("P.FIRST_NAME like ?"); ORDER_BY("P.ID"); ORDER_BY("P.FULL_NAME"); }}.toString(); }
本人以前发过一篇文章,试图用Java注释的方式来支持多行文本,以方便SQL的定位(见https://my.oschina.net/drinkjava2/blog/892309),但是那篇文章中的方法有三个问题,一是Java文件在布署时,要手工拷贝一份到resource目录中去,不方便;二是不小心注释会被编辑器给格式化了;三是需要手工在程序中给出Java源文件的绝对路径。最近绞尽脑汁,又找到一个好一点的方法,依然是利用Java注释,但是没有以上三个缺点了:
做法:
1. 在pom.xml中添加一个build-helper-maven-plugin插件,将resource目录加入编译范围,插件会将所有在resources下的所有Java文件当作资源文件打包,这样就不用再手工拷贝一份到resouces目录下去了。而且经实测,这个插件在运行 mvn eclipse:eclipse 命令时能正确添加resources目录到eclipse中的编译目录:
<build> <plugins> ...... <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>build-helper-maven-plugin</artifactId> <version>1.7</version> <executions> <execution> <id>add-source</id> <phase>generate-sources</phase> <goals> <goal>add-source</goal> </goals> <configuration> <sources> <source>src/main/resources</source> <source>src/test/resources</source> </sources> </configuration> </execution> </executions> </plugin> <plugins> </build>
2. 写一个工具类,用来读取Java源码, 在Eclipse环境下时,从project/src/main或project/src/text下读,在布署环境下时,从类根目录下读取(因为resources下的Java文件被当作资源文件打包):
public class TextUtils { private static final Map<Class<?>, String> javaFileCache = new HashMap<Class<?>, String>(); @SuppressWarnings("all") public static String getJavaSourceCodeUTF8(Class<?> clazz) { return getJavaSourceCode(clazz, "UTF-8"); } @SuppressWarnings("all") public static String getJavaSourceCode(Class<?> clazz, String encoding) { if (javaFileCache.containsKey(clazz)) return javaFileCache.get(clazz); String classPathName = StringUtils.substringBefore(clazz.getName(), "$");// aa.bb.Cc classPathName = "/" + StringUtils.replace(classPathName, ".", "/");// aa/bb/Cc String fileName = classPathName + ".java";// /aa/bb/Cc.java InputStream inputStream = null; try { inputStream = TextUtils.class.getResourceAsStream(fileName); if (inputStream == null) {// Not found, it means in eclipse environment File file = new File(clazz.getResource(classPathName + ".class").getFile()); String absPath = file.getAbsolutePath(); absPath = StringUtils.replace(absPath, "\\", "/"); String projectFolder = StringUtils.substringBefore(absPath, "/target/classes/"); String realPath = projectFolder + "/src/main/resources" + classPathName + ".java"; file = new File(realPath); if (!file.exists()) { realPath = projectFolder + "/src/test/resources" + classPathName + ".java"; file = new File(realPath); } if (!file.exists()) throw new IOException("Can not find " + clazz.getName() + ".java in resources folder"); inputStream = new FileInputStream(file); if (inputStream == null) throw new IOException("Can not find " + clazz.getName() + ".java in resources folder"); } ByteArrayOutputStream result = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) != -1) result.write(buffer, 0, length); String javaSrc = result.toString(encoding); javaFileCache.put(clazz, javaSrc); return javaSrc; } catch (IOException e) { throw new RuntimeException(e); } finally { if (inputStream != null) try { inputStream.close(); } catch (IOException e) { throw new RuntimeException(e); } } } }
3. 在src/main/resources或src/test/resources目录下添加需要访问源码的Java文件如:
public interface TextSample1 { @SQL("select *from User") public <T> T retrieveAllUsers(); @Handler(MapListHandler.class) //DbUtils自带的 public <T> T retrieveUserById(String firstName, String lastName); /*- SELECT P.ID, P.USERNAME, P.PASSWORD, P.FULL_NAME P.LAST_NAME,P.CREATED_ON, P.UPDATED_ON FROM PERSON P, ACCOUNT A INNER JOIN DEPARTMENT D on D.ID = P.DEPARTMENT_ID INNER JOIN COMPANY C on D.COMPANY_ID = C.ID WHERE (P.ID = A.ID AND P.FIRST_NAME like #{firstName}) OR (P.LAST_NAME like #{lastName}) GROUP BY P.ID HAVING (P.LAST_NAME like #{lastName}) OR (P.FIRST_NAME like #{firstName}) ORDER BY P.ID, P.FULL_NAME */ }
4.在程序的任何地方,就可以用以下代码获取java的源码,以便做进一步处理了(抽取出对应方法的多行文本,这一步我还没有做,但1到4都测试过了,所以想当然是没问题的)。
TextUtils.getJavaSourceCodeUTF8(TextSample1.class)
对了,差点忘了说,所有注释必须用/*-开头,这样就不会被Eclipse给误格式化了。
以上方法只在Eclipse+Maven 开发方式下实测过,其它编辑器不在考虑范围内。