Mybatis多参数查询映射

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
[java] view plaincopyprint?
<span style="font-weight: normal;"><span style="font-family:Microsoft YaHei;font-size:14px;">User getUserById(int id); 
 
select * from <TABLE> where id = #{id} 
// or 
select * from <TABLE> where id = #{abdc} 
// or 
select * 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
[java] view plaincopyprint?
<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
[java] view plaincopyprint?
<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
[java] view plaincopyprint?
<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.
[java] view plaincopyprint?
<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
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<span style="font-family:Microsoft YaHei;font-size:14px;">org.apache.ibatis.binding.MapperMethod 
private 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
[java] view plaincopyprint?
<span style="font-family:Microsoft YaHei;font-size:14px;">org.apache.ibatis.executor.parameter.DefaultParameterHandler 
public 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);   
            }   
        }   
    }