mybatis参数映射

来源：互联网发布：海尔网络电视打开蓝屏编辑：程序博客网时间：2024/05/18 11:28

mybatis参数映射(?)

规则

非@Param注解参数时可使用
```
 #{参数位置[0..n-1]}
```
或者
```
 #{param[1..n]}
```
如果参数类型是自定义对象(bean)时,只需加上.对象属性即可
```
 #{参数位置[0..n-1].对象属性}
 #{param[1..n].对象属性}
```
特别的，如果非注解参数只有一个时，可使用
```
 #{任意字符}
```
来访问参数
@Param的作用是设置参数别名。设置后的参数只能通过
```
 #{注解别名}
```
或者
```
 #{param[1..n]}     
```
如果参数类型是自定义对象(bean)时,只需加上.对象属性即可
```
  #{注解别名.属性}
  #{param[1..n].属性}
```
来访问参数

示例

为了明确上述规则，我们的示例具体细分了各种情况进行展示。

非注解型

一个参数

<span style="font-weight: normal;"><span style="font-family:Microsoft YaHei;font-size:14px;">User getUserById(int id);select * from <TABLE> where id = #{id}// orselect * from <TABLE> where id = #{abdc}// orselect * from <TABLE> where id = #{param1}User getUser(User user); // user.getName user.getAge select * from <TABLE> where name = #{name} and age = #{age}</span></span>

多个参数

<span style="font-family:Microsoft YaHei;font-size:14px;">User getUser(String name, int age);  select * from <TABLE> where name = #{0} and age = #{1}  // or  select * from <TABLE> where name = #{param1} and age = #{param2}  User getUser(User usr, int flag);  select * from <TABLE> where name = #{0.name} and age = {0.age} and flag = #{1}  // or  select * from <TABLE> where name = #{param1.name} and age = {param1.age} and flag = #{param2}</span>

注解型

一个参数

<span style="font-family:Microsoft YaHei;font-size:14px;">User getUserById(@Param(value="keyId") int id);  select * from <TABEL> where id = #{keyId}  // or  select * from <TABLE> where id = #{param1}  User getUser(@Param(value="user") User user); // user.getName user.getAge  select * from <TABLE> where name = #{user.name} and age = #{user.age}  // or  select * from <TABLE> where name = #{param1.name} and age = #{param1.age}</span>

多个参数

<span style="font-family:Microsoft YaHei;font-size:14px;">User getUser(@Param(value="xm") String name, @Param(value="nl") int age);  select * from <TABLE> where name = #{xm} and age = #{nl}  // or  select * from <TABLE> where name = #{param1} and age = #{param2}  // or  select * from <TABLE> where name = #{xm} and age = #{param2}  User getUser(@Param(value="usr") User user, @Param(value="tag") int flag); select * from <TABLE> where name = #{usr.name} and age = #{usr.age} and flag = #{tag}  // or  select * from <TABLE> where name = #{param1.name} and age = #{param1.age} and flag = #{param2}  // or  select * from <TABLE> where name = #{usr.name} and age = #{param1.age} and flag = #{param2}</span>

非注解和注解型混合型

当采用部分参数使用@Param注解时，参数注释为将以上两种情况结合起来即可.

<span style="font-family:Microsoft YaHei;font-size:14px;">User getUser(String name, @Param(value="nl") age, int gendar);  // 对于age的访问不能是 #{1} 只能是 #{param2} | #{nl}  select * from <TABLE> where name = #{0} and age = #{nl} and gendar = #{param3)</span>

框架主要映射处理代码

参数的获取

<span style="font-family:Microsoft YaHei;font-size:14px;">org.apache.ibatis.binding.MapperMethodprivate Object getParam(Object[] args) {      final int paramCount = paramPositions.size();      // 无参数      if (args == null || paramCount == 0) {          return null;      // 无注解并参数个数为1      } else if (!hasNamedParameters && paramCount == 1) {          return args[paramPositions.get(0)];      } else {          Map<String, Object> param = new MapperParamMap<Object>();          for (int i = 0; i < paramCount; i++) {              param.put(paramNames.get(i), args[paramPositions.get(i)]);      }      // issue #71, add param names as param1, param2...but ensure backward compatibility      // 这就是 #{param[1..n]} 的来源      for (int i = 0; i < paramCount; i++) {          String genericParamName = "param" + String.valueOf(i + 1);          if (!param.containsKey(genericParamName)) {              param.put(genericParamName, args[paramPositions.get(i)]);          }      }      return param;      }  }</span>

SQL预编译参数设置

<span style="font-family:Microsoft YaHei;font-size:14px;">org.apache.ibatis.executor.parameter.DefaultParameterHandlerpublic void setParameters(PreparedStatement ps) throws SQLException {      ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());      List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();      if (parameterMappings != null) {          MetaObject metaObject = parameterObject == null ? null : configuration.newMetaObject(parameterObject);          for (int i = 0; i < parameterMappings.size(); i++) {              ParameterMapping parameterMapping = parameterMappings.get(i);              if (parameterMapping.getMode() != ParameterMode.OUT) {                  Object value;                  String propertyName = parameterMapping.getProperty();                  PropertyTokenizer prop = new PropertyTokenizer(propertyName);                  if (parameterObject == null) {                      value = null;                  } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {                      value = parameterObject;                  } else if (boundSql.hasAdditionalParameter(propertyName)) {                      value = boundSql.getAdditionalParameter(propertyName);                  } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)            && boundSql.hasAdditionalParameter(prop.getName())) {                      value = boundSql.getAdditionalParameter(prop.getName());                      if (value != null) {                          value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));                      }              } else {                  value = metaObject == null ? null : metaObject.getValue(propertyName);              }              TypeHandler typeHandler = parameterMapping.getTypeHandler();              if (typeHandler == null) {                  throw new ExecutorException("There was no TypeHandler found for parameter " + propertyName + " of statement " + mappedStatement.getId());              }              JdbcType jdbcType = parameterMapping.getJdbcType();              if (value == null && jdbcType == null) jdbcType = configuration.getJdbcTypeForNull();                  typeHandler.setParameter(ps, i + 1, value, jdbcType);              }          }      }  }</span>