初识BoundSQL

参考文章
MyBatis原理系列(六)-手把手带你了解BoundSql的创建过程

什么是BoundSQL

原码：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.apache.ibatis.mapping;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.property.PropertyTokenizer;
import org.apache.ibatis.session.Configuration;

public class BoundSql {

	// 最终解析的SQL，Mybatis将#{}和${}解析后的sql，其中#{}会被解析为?
    private String sql;
    // 参数映射
    private List<ParameterMapping> parameterMappings;
    // 参数对象
    private Object parameterObject;
    // 额外的参数
    private Map<String, Object> additionalParameters;
    // 元数据参数
    private MetaObject metaParameters;

    public BoundSql(Configuration configuration, String sql, List<ParameterMapping> parameterMappings, Object parameterObject) {
        this.sql = sql;
        this.parameterMappings = parameterMappings;
        this.parameterObject = parameterObject;
        this.additionalParameters = new HashMap();
        this.metaParameters = configuration.newMetaObject(this.additionalParameters);
    }

    public String getSql() {
        return this.sql;
    }

    public List<ParameterMapping> getParameterMappings() {
        return this.parameterMappings;
    }

    public Object getParameterObject() {
        return this.parameterObject;
    }

    public boolean hasAdditionalParameter(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        String indexedName = prop.getIndexedName();
        return this.additionalParameters.containsKey(indexedName);
    }

    public void setAdditionalParameter(String name, Object value) {
        this.metaParameters.setValue(name, value);
    }

    public Object getAdditionalParameter(String name) {
        return this.metaParameters.getValue(name);
    }
}

BoundSql就是对解析后的SQL的描述，包括对动态标签的解析，并且将**#{}解析为占位符?**，还包含参数的描述信息。可以看做是解析后的sql描述对象。

to be continued…