mybatis详解学习之mybatis中非代理模式设置查询参数时是忽略类型的

非代理使用Mybatis

一、环境搭建

1、pom文件

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.mybatis.source.test</groupId>
	<artifactId>mybatis-pro</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<properties>
		<slf4j-api.version>1.7.25</slf4j-api.version>
		<logback.version>1.1.7</logback.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>ognl</groupId>
			<artifactId>ognl</artifactId>
			<version>3.0.8</version>
		</dependency>
		<dependency>
			<groupId>org.javassist</groupId>
			<artifactId>javassist</artifactId>
			<version>3.24.1-GA</version>
		</dependency>
		<dependency>
			<groupId>org.mybatis</groupId>
			<artifactId>mybatis</artifactId>
			<version>3.3.0-SNAPSHOT</version>
		</dependency>

		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>${slf4j-api.version}</version>
		</dependency>
		<dependency>
			<groupId>ch.qos.logback</groupId>
			<artifactId>logback-core</artifactId>
			<version>${logback.version}</version>
		</dependency>
		<dependency>
			<groupId>ch.qos.logback</groupId>
			<artifactId>logback-access</artifactId>
			<version>${logback.version}</version>
		</dependency>
		<dependency>
			<groupId>ch.qos.logback</groupId>
			<artifactId>logback-classic</artifactId>
			<version>${logback.version}</version>
		</dependency>

		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>

		<dependency>
			<groupId>commons-logging</groupId>
			<artifactId>commons-logging</artifactId>
			<version>1.2</version>
		</dependency>
		<dependency>
			<groupId>org.apache.logging.log4j</groupId>
			<artifactId>log4j-core</artifactId>
			<version>2.13.3</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.16</version>
		</dependency>


	</dependencies>
</project>

2、Mybatis主配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="lazyLoadingEnabled" value="false"/>
    </settings>
    <typeAliases>
        <typeAlias alias="role" type="com.mybatis.learn.bean.Role"/>
    </typeAliases>
    <typeHandlers>
        <typeHandler jdbcType="VARCHAR" javaType="string" handler="com.mybatis.learn.handler.MyStringHandler"/>
    </typeHandlers>
    <!-- 定义数据库的信息，默认使用development数据库构建环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/project_crowd?serverTimezone=UTC" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>
    <!-- 定义映射器 -->
    <mappers>
        <package name="com.mybatis.learn.mapper" />
    </mappers>

</configuration>

3、日志配置文件

log4j.rootLogger=DEBUG,stdout
log4j.logger.org.mybatis=DUBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.logDailyFile.layout.ConversionPattern = %5p %d %C:%m%n

4、mapper配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.source.test.mapper.RoleMapper">
	<resultMap type="role" id="roleMap">
		<id column="id" property="id" javaType="long" jdbcType="BIGINT" />
		<result column="role_name" property="roleName" javaType="string" jdbcType="VARCHAR" />
		<result column="note" property="note" typeHandler="com.mybatis.source.test.handler.MyStringHandler" />
	</resultMap>
	
	<select id="queryRolesByCondition" parameterType="com.mybatis.source.test.bean.Role" resultMap="roleMap">
		select * from role where
        1=1
        <if test="id!=null">
            and id=#{id,jdbcType=BIGINT}
        </if>
        <if test="roleName!=null">
            and role_name=#{roleName,jdbcType=BIGINT}
        </if>
        <if test="note!=null">
            and note=#{note,jdbcType=BIGINT}
        </if>
        and tenant_id=#{tenantId,jdbcType=VARCHAR}
	</select>
	
	<select id="getRole" parameterType="long" resultMap="roleMap">
		select
		id,role_name as roleName,note from role where id=#{id}
	</select>
	<select id="findRole" parameterType="long" resultMap="roleMap">
		select
		id,role_name,note from role where role_name like CONCAT('%',#{roleName
		javaType=string,
		jdbcType=VARCHAR,typeHandler=com.mybatis.source.test.handler.MyStringHandler},'%')
	</select>
	<insert id="insertRole" parameterType="role">
		insert into
		role(role_name,note) value(#{roleName},#{note})
	</insert>
	<delete id="deleteRole" parameterType="long">
		delete from role where
		id=#{id}
	</delete>
</mapper>

5、mapper接口

package com.mybatis.source.test.mapper;

import java.util.List;

import com.mybatis.source.test.bean.Role;

public interface RoleMapper {
	public Role getRole(Long id);
    public Role findRole(String roleName);
    public int deleteRole(Long id);
    public int insertRole(Role role);
    
    public List<Role> queryRolesByCondition(Role role);
}

二、非代理方式代码执行

1、测试代码

package com.mybatis.source.test.Main;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.mybatis.source.test.bean.Role;
import com.mybatis.source.test.mapper.RoleMapper;

public class Main {
	public static void main(String[] args) {
		String resource = "mybatis-config.xml";
		InputStream inputStream = null;
		try {
			inputStream = Resources.getResourceAsStream(resource);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		SqlSessionFactory sqlSessionFactory = null;
		sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		SqlSession sqlSession = null;
		try {
			sqlSession = sqlSessionFactory.openSession();

			Map<String,Object> param=new HashMap<>();
			param.put("id", 1);
			List<Role> list = sqlSession.selectList("com.mybatis.source.test.mapper.RoleMapper.queryRolesByCondition", param);

			sqlSession.commit();

		} catch (Exception e) {
			sqlSession.rollback();
			e.printStackTrace();
		} finally {
			sqlSession.close();
		}
	}
}

2、执行结果

com.mybatis.source.test.mapper.RoleMapper.queryRolesByCondition - ==> 
Preparing: select * from role where 1=1 and id=? and tenant_id=? 
com.mybatis.source.test.mapper.RoleMapper.queryRolesByCondition - ==> Parameters: 1(Integer), null
com.mybatis.source.test.mapper.RoleMapper.queryRolesByCondition - <==      Total: 0

3、结果分析

RoleMapper.queryRolesByCondition接口的入参是Role，但是在测试代码中，我们传入的是Map对象，发现代码也能运行。

其原因是因为参数值的获取是通过MetaObject工具类来获取的，代码如下：

//设置参数
  @Override
  public void setParameters(PreparedStatement ps) throws SQLException {
    ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
    List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
    if (parameterMappings != null) {
      //循环设参数
      for (int i = 0; i < parameterMappings.size(); i++) {
        ParameterMapping parameterMapping = parameterMappings.get(i);
        if (parameterMapping.getMode() != ParameterMode.OUT) {
          //如果不是OUT，才设进去
          Object value;
          String propertyName = parameterMapping.getProperty();
          if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
            //若有额外的参数, 设为额外的参数
            value = boundSql.getAdditionalParameter(propertyName);
          } else if (parameterObject == null) {
            //若参数为null，直接设null
            value = null;
          } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
            //若参数有相应的TypeHandler，直接设object
            value = parameterObject;
          } else {
            //除此以外，MetaObject.getValue反射取得值设进去
            MetaObject metaObject = configuration.newMetaObject(parameterObject);
            value = metaObject.getValue(propertyName);
          }
          TypeHandler typeHandler = parameterMapping.getTypeHandler();
          JdbcType jdbcType = parameterMapping.getJdbcType();
          if (value == null && jdbcType == null) {
            //不同类型的set方法不同，所以委派给子类的setParameter方法
            jdbcType = configuration.getJdbcTypeForNull();
          }
          typeHandler.setParameter(ps, i + 1, value, jdbcType);
        }
      }
    }
  }

4、MetaObject测试

采用MetaObject工具类，并不关心对象是什么样的类型，只要给出对象中有什么属性，就可以通过工具类拿到对象对应的属性的值

package com.mybatis.learn.main;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class Person{
    private String name;
    private String address;

    public Person(String name, String address) {
        this.name = name;
        this.address = address;
    }
}
public class MetaObjectTest {
    static SqlSessionFactory sqlSessionFactory = null;

    static{
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static void main(String[] args) {
        List<String> fieldNameList=new ArrayList<>();
        fieldNameList.add("name");
        fieldNameList.add("address");
        Map<String,String> map=new HashMap<>();
        map.put("name","张三");
        map.put("address","杭州市");
        //可以访问map中属性为name与address的值
        printFieldValue(map,fieldNameList);
        System.out.println("+++++++++++++++++++++++++");
        Person person=new Person("王五","北京市");
        // 可以访问对象中属性为name与address的值
        printFieldValue(person,fieldNameList);

    }

    public static void printFieldValue(Object obj, List<String> fieldNames){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        Configuration configuration = sqlSession.getConfiguration();
        MetaObject metaObject=configuration.newMetaObject(obj);
        for (String fieldName:fieldNames){
            Object value = metaObject.getValue(fieldName);
            System.out.println(value);
        }
    }
    
    // 模拟MetaObject对象的getValue方法
     public static void printFieldByReflect(Object obj, List<String> fieldNames){
        if(obj instanceof Map){
            Map<String,Object> map=( Map<String,Object>)obj;
            for(String fieldName:fieldNames){
                System.out.println(map.get(fieldName));
            }

        }else if(obj instanceof Collection){

        }else if(obj != null && obj.getClass().isArray()){

        }else{
            Class<?> aClass = obj.getClass();
            for(String fieldName:fieldNames){
                try{
                    Field field = aClass.getDeclaredField(fieldName);
                    field.setAccessible(true);
                    Object o = field.get(obj);
                    System.out.println(o);

                }catch (Exception e){
                    e.printStackTrace();
                }

            }
        }


    }


}

所以在Mybatis对象设置参数值时，一般并不会去校验对象的类型，只关注对象中是否有相应的属性。