Java 我可以使用MyBatis生成动态SQL而不执行它吗?
我有一些复杂的查询需要使用一些可选的过滤器来构建,MyBatis似乎是生成动态SQL的理想候选者 但是,我仍然希望查询与应用程序的其余部分(不使用MyBatis)在相同的框架中执行Java 我可以使用MyBatis生成动态SQL而不执行它吗?,java,dynamic-sql,mybatis,Java,Dynamic Sql,Mybatis,我有一些复杂的查询需要使用一些可选的过滤器来构建,MyBatis似乎是生成动态SQL的理想候选者 但是,我仍然希望查询与应用程序的其余部分(不使用MyBatis)在相同的框架中执行 所以我希望严格使用MyBatis来生成SQL,但从那以后,我会使用我的应用程序的其余部分来实际执行它。这可能吗?如果是,怎么做?虽然MyBatis的设计是在构建查询后执行查询,但您可以利用它的配置和一点“内部知识”来获得所需的信息 MyBatis是一个非常好的框架,不幸的是它缺乏文档方面的内容,所以源代码是您的朋友。
所以我希望严格使用MyBatis来生成SQL,但从那以后,我会使用我的应用程序的其余部分来实际执行它。这可能吗?如果是,怎么做?虽然MyBatis的设计是在构建查询后执行查询,但您可以利用它的配置和一点“内部知识”来获得所需的信息 MyBatis是一个非常好的框架,不幸的是它缺乏文档方面的内容,所以源代码是您的朋友。如果你仔细研究,你应该会碰到以下类:
org.apache.ibatis.mapping.MappedStatement
和org.apache.ibatis.mapping.BoundSql
,它们是构建动态SQL的关键角色。下面是一个基本用法示例:
MySQL表user
中包含此数据:
name login
----- -----
Andy a
Barry b
Cris c
用户
类别:
package pack.test;
public class User {
private String name;
private String login;
// getters and setters ommited
}
UserService
接口:
package pack.test;
public interface UserService {
// using a different sort of parameter to show some dynamic SQL
public User getUser(int loginNumber);
}
UserService.xml
mapper文件:
<mapper namespace="pack.test.UserService">
<select id="getUser" resultType="pack.test.User" parameterType="int">
<!-- dynamic change of parameter from int index to login string -->
select * from user where login = <choose>
<when test="_parameter == 1">'a'</when>
<when test="_parameter == 2">'b'</when>
<otherwise>'c'</otherwise>
</choose>
</select>
</mapper>
AppTester
显示结果:
package pack.test;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class AppTester {
private static String CONFIGURATION_FILE = "sqlmap-config.xml";
public static void main(String[] args) throws Exception {
Reader reader = null;
SqlSession session = null;
try {
reader = Resources.getResourceAsReader(CONFIGURATION_FILE);
session = new SqlSessionFactoryBuilder().build(reader).openSession();
UserService userService = session.getMapper(UserService.class);
// three users retreived from index
for (int i = 1; i <= 3; i++) {
User user = userService.getUser(i);
System.out.println("Retreived user: " + user.getName() + " " + user.getLogin());
// must mimic the internal statement key for the mapper and method you are calling
MappedStatement ms = session.getConfiguration().getMappedStatement(UserService.class.getName() + ".getUser");
BoundSql boundSql = ms.getBoundSql(i); // parameter for the SQL statement
System.out.println("SQL used: " + boundSql.getSql());
System.out.println();
}
} finally {
if (reader != null) {
reader.close();
}
if (session != null) {
session.close();
}
}
}
}
Retreived user: Andy a
SQL used: select * from user where login = 'a'
Retreived user: Barry b
SQL used: select * from user where login = 'b'
Retreived user: Cris c
SQL used: select * from user where login = 'c'
只需补充Bogdan的正确答案:如果您认为接口具有更复杂的签名,则需要使用getter将JavaBean传递给接口参数的
getBoundSql()
假设您希望根据登录号码和/或用户名查询用户。您的界面可能如下所示:
package pack.test;
public interface UserService {
// using a different sort of parameter to show some dynamic SQL
public User getUser(@Param("number") int loginNumber, @Param("name") String name);
}
// get parameterized query
MappedStatement ms = configuration.getMappedStatement("MyMappedStatementId");
BoundSql boundSql = ms.getBoundSql(parameters);
System.out.println("SQL" + boundSql.getSql());
// SELECT species FROM animal WHERE name IN (?, ?) or id = ?
我省略了Mapper代码,因为它与本次讨论无关,但您在AppTester中的代码应该是:
[...]
final String name = "Andy";
User user = userService.getUser(i, name);
System.out.println("Retreived user: " + user.getName() + " " + user.getLogin());
// must mimic the internal statement key for the mapper and method you are calling
MappedStatement ms = session.getConfiguration().getMappedStatement(UserService.class.getName() + ".getUser");
BoundSql boundSql = ms.getBoundSql(new Object() {
// provide getters matching the @Param's in the interface declaration
public Object getNumber() {
return i;
}
public Object getName() {
return name;
}
});
System.out.println("SQL used: " + boundSql.getSql());
System.out.println();
[...]
每个人都知道如何使用BoundSql.getSql()从MyBatis获取参数化查询字符串,如下所示:
package pack.test;
public interface UserService {
// using a different sort of parameter to show some dynamic SQL
public User getUser(@Param("number") int loginNumber, @Param("name") String name);
}
// get parameterized query
MappedStatement ms = configuration.getMappedStatement("MyMappedStatementId");
BoundSql boundSql = ms.getBoundSql(parameters);
System.out.println("SQL" + boundSql.getSql());
// SELECT species FROM animal WHERE name IN (?, ?) or id = ?
但现在你需要等式的另一半,对应于问号的值列表:
// get parameters
List<ParameterMapping> boundParams = boundSql.getParameterMappings();
String paramString = "";
for(ParameterMapping param : boundParams) {
paramString += boundSql.getAdditionalParameter(param.getProperty()) + ";";
}
System.out.println("params:" + paramString);
// "Spot;Fluffy;42;"
//获取参数
List boundParams=boundSql.getParameterMappings();
字符串paramString=“”;
用于(参数映射参数:边界参数){
paramString+=boundSql.getAdditionalParameter(param.getProperty())+“;”;
}
System.out.println(“参数:+paramString”);
//“斑点;毛茸茸的;42;”
现在,您可以将其序列化以发送到别处运行,也可以将其打印到日志中,以便将它们缝合在一起并手动运行查询
*未测试的代码,可能是轻微的类型问题或类似问题mybatis版本为3.4.5 工具类 要将映射器转换为sql,需要映射器接口类、方法名称、参数和sqlSession
package util;
import java.lang.reflect.Method;
import java.text.DateFormat;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.regex.Matcher;
import org.apache.ibatis.binding.MapperMethod.MethodSignature;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.type.TypeHandlerRegistry;
import org.springframework.util.CollectionUtils;
/**
* @author zwxbest - 19-4-25
*/
public class SqlUtil {
public static String showSql(SqlSession sqlSession, Class mapperInterface, String methodName,
Object[] params) {
Configuration configuration = sqlSession.getConfiguration();
MappedStatement ms = configuration.getMappedStatement(
mapperInterface.getName() + "." + methodName);
Method sqlMethod = null;
//find method equals methodName
for (Method method : mapperInterface.getDeclaredMethods()) {
if (method.getName().equals(methodName)) {
sqlMethod = method;
break;
}
}
if (sqlMethod == null) {
throw new RuntimeException("mapper method is not found");
}
MethodSignature method = new MethodSignature(configuration, mapperInterface, sqlMethod);
Object paramObject = method.convertArgsToSqlCommandParam(params);
BoundSql boundSql = ms.getBoundSql(paramObject);
Object parameterObject = boundSql.getParameterObject();
List<ParameterMapping> parameterMappings = boundSql
.getParameterMappings();
String sql = boundSql.getSql().replaceAll("[\\s]+", " ");
if (!CollectionUtils.isEmpty(parameterMappings) && parameterObject != null) {
TypeHandlerRegistry typeHandlerRegistry = configuration
.getTypeHandlerRegistry();
if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
sql = sql.replaceFirst("\\?",
Matcher.quoteReplacement(getParameterValue(parameterObject)));
} else {
MetaObject metaObject = configuration.newMetaObject(
parameterObject);
for (ParameterMapping parameterMapping : parameterMappings) {
String propertyName = parameterMapping.getProperty();
if (metaObject.hasGetter(propertyName)) {
Object obj = metaObject.getValue(propertyName);
sql = sql
.replaceFirst("\\?", Matcher.quoteReplacement(getParameterValue(obj)));
} else if (boundSql.hasAdditionalParameter(propertyName)) {
Object obj = boundSql.getAdditionalParameter(propertyName);
sql = sql
.replaceFirst("\\?", Matcher.quoteReplacement(getParameterValue(obj)));
} else {
sql = sql.replaceFirst("\\?", "missing");
}
}
}
}
return sql;
}
/**
* if param's type is `String`,add single quotation<br>
*
* if param's type is `datetime`,convert to string and quote <br>
*/
private static String getParameterValue(Object obj) {
String value = null;
if (obj instanceof String) {
value = "'" + obj.toString() + "'";
} else if (obj instanceof Date) {
DateFormat formatter = DateFormat
.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.CHINA);
value = "'" + formatter.format(new Date()) + "'";
} else if (obj instanceof LocalDateTime) {
value = "\'" + ((LocalDateTime) obj)
.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")) + "\'";
} else {
if (obj != null) {
value = obj.toString();
} else {
value = "";
}
}
return value;
}
}
对我来说,它显示的是
?
,而不是实际值。e、 g.其中login=?
。有什么办法吗?谢谢(我没有使用mapper类)